To bring everyone up to speed on network topology in games:
GTA Online uses what's called a peer-to-peer mesh network setup. This means that every PC/console on a connected session is talking to every other PC/console in that session. The preferred alternative for most multiplayer games is sever-client, where in every PC/console is talking with a single server.
With p2p mesh, this means that everyone shares authority. What this translates to is that a server is not the single authority checking for malicious activity, much of which anyone who has played GTA Online for is familiar with. This also means that anyone with the know-how can figure out what IP every other person is connecting from. This can lead to other malicious activity outside of the game.
But standing up dedicated servers costs money. Why not avoid that?
There are plenty of cases to be made where peer-to-peer connectivity makes sense, especially from a cost-savings perspective. But in some cases, like GTA Online, the benefits/gains from using a server-client setup far outweigh the costs.
So, in no particular order:

What Dedicated Servers Would Have Brought to RS/T2:

More purchases of cash in the Social store.
We'll start with the obvious here. When someone can get into a game and ask about [redacted method of obtaining money] and get a response 50% of the time, it's an obvious miss on being able to purchase prepaid in-game credit cards from the store. There's no incentive. And if they don't want to ask someone to do it, they can do it themselves.
Higher volume of Twitch streamers.
It seems easily correlated, but Twitch's research shows that livestreaming leads to better game sales. The reason this isn't streamed as broadly is because not everyone can get enough reliable people for a heist. Private sessions can be invaded by the same people who also [redacted method of obtaining money]. This is regardless of the privacy of a lobby, because those same people can find a unique identifier on the public Rockstar social site and join it, regardless of whether or not they're a friend or a crew member-- or simply not invited.
What this translates to are people who have such a low bar to pass to join a streamer's game and hold the experience hostage, crash the session or do any other number of malicious things. They can also impersonate people and send messages as them. So this further leads to things like not being able to do:
Twitch Rivals streams between competing streamer teams.
Imagine this: the game is pretty solidly protected from people who [redacted method of obtaining money] and those incidents they generate are rare, and when they do pop up, they're punished. So, streaming this game is far more viable. Competitive crews start forming, and Rockstar promotes an event with streamers where they're able to host lobbies and get 24, 36 or even 48 streamers in one session running 12 different crews for things like:

• Business goods battles
• Arena wars
• Deathmatches
• Races

And so on and so forth. But because items have to be obtained through legitimate game mechanics, it also implements a grind. Maybe these groups/crews have been running for a while. But then you'd also be able to do:
Streamer Drops through Connected Accounts
We've seen other games do this, where viewers can get "drops" into their game by watching the streamer play it. These drops could have been literally anything that was on the Diamond Casino Wheel of Fortune. It could have even been a bonus spin at the wheel, to encourage getting the player in the game.
The Long-Term, Sharded MMO Experience
This translates to cash because people would be continually playing the game, which means more people paying for in-game cash and general popularity because more people would be streaming it, but this is the bigger buyback to the player, too.
Imagine a crew that worked hard at completing a certain set of heists on hard difficulty, no deaths, consecutive. Four people who are streaming their attempt like people do for raid bosses. And their reward was a unique yacht only available for them.
A ranked arena war system that awarded players who got 100 wins with a unique vehicle or livery.
The system could have been adjusted to make some things a grind. Making that money with friends, and then knowing that if someone had a high-end apartment, much less a casino penthouse, that they earned it through blood, sweat and hard work.
Powerful crews that were running around and happen to land on the same lobby and an all-out war with tactics, reinforcements and a consideration of cash drain to get the win in Los Santos.
These are the things that Rockstar and Take2 missed out on by not having dedicated servers with protections against [redacted method of obtaining money]. They were on the verge of greatness. They were this close. And I know that a lot of this translates over for Red Dead Online, too.

Is It Too Late to Do All of This?

No, I don't think so. If RockstaTake2 were to seek redemption from this, here's what they'd have to do:
Implement a dedicated server gamemode, and only allow characters created for this game mode specifically.
If people want to continue messing around in peer-to-peer sessions, maybe they allow that for a time before slowly forcing people over (because it's all about that money, right?). But create a new character (or duplicate the looks of one), and make it only available for play on controlled, dedicated servers.
You can even put Ye Olde GTA 5 spin on it and have Lester come in and say, "Yeah, I know the simulation was pretty fucked, right? It got hacked by kids on Christmas break. But anyway, now that you know what's possible out there in this stupid, god-forsaken world, well... uh, perhaps it's time we started making some money. And you remember Fleeca, right?"
Then people start off fresh, and work on earning things through the grind. I promise you, that'll net you some untold money and viewership. And I have faith enough that even if you made a very solid push into authoritative client-host conversion from peer-to-peer mesh, allowing the authoritative client-host to be controlled by Rockstar servers, you'd get something out of it.
And I will put a disclaimer on here: I don't know if the game engine is so archaic that it wouldn't allow for this kind of change. And if that is indeed the case, then the only thing that I can say is you missed out on all of the above by choosing to design what you did, because it is a proprietary engine.
But if you can, imaginary Rockstar or Take2 directory reading this, please, I implore you. Push for the change. This has been one of the best social games for me during lockdown, and I can't overstate how much everyone will benefit from this.
Sincerely,
~The Village Idiot

Executive Summary / TLDR:

• Heists are awesome
• Many missions are awesome
• Freemode is a foaming shitblizzard of cheats and griefers

​

Long winded ramble

So, basically this is a great game that hides its greatness under some pretty fundamental design flaws like having an inadequate security model and an new user experience that showcases of all the game's worst aspects while carefully hiding the good bits.
Heists are great, but they need some work. Fleeca is about right, the progression ones go off the rails immediately though. The Prison Break is one of the hardest heists in the game, and most players seem to get permanently stuck on it and give up. I don't blame them. It's a bitch with a pickup group and the payoff is absolutely not worth it.
Personally, I didn't get past the horrific garbage truck setup in Series A. My little merry band have been doing the Casino one though (it's wonderful), and I discovered that being a looter on someone else's Cayo Perico heist is so lucrative (for both) and fun that I saved up for my own sub and penthouse and can now do that wondrous heist myself.
Speaking of Cayo, I think it needs some entry point rotation the way the Casino does it. You shouldn't be able to just repeat the sewer pipe entry point. Entry and exit points you've used recently should be closed off and then have extra guards, encouraging and rewarding variation in play.
For the storyline ones the game badly needs a new setting for voice comms so people can easily use those for four-person heists without also hearing the confused 9yos in Freemode asking where their car is. (Why the HELL are children playing this game? Oh my god!) At the moment it's like "friends&crew" or "everyone" or something and that is just not good enough. The storyline heists and setups are a lot easier with active communication, and most pickup groups don't even use text chat. That's a huge problem.
I'd also tweak the rewards and difficulty, and put in a mechanism to encourage players to make more than one attempt before quitting. Not to mention letting groups recruit replacements without having to completely re-form. Too many players drop after a fail or two making this part of the game a frustrating mess if you don't bring your own heist crew.
Missions are another weird one. There are easily a hundred brilliant missions in the game, and most people play the same 6-10 missions over and over and never discover the great ones. This is 100% due to game design and the fact that the matchmaking system keeps shoving people into the most commonly done missions. Also the "continue" page keeps showing you missions you've already done, instead of popular ones you haven't. There's some wonderful content in there but it's hidden behind what comes across as a very shallow game with a handful of crappy missions.
Freemode is horrible, and it's mostly due to the fact that the game relies too heavily on peer-to-peer with zero verification. There is nothing wrong with using PTP for positional data, which is the majority of traffic, but anything involving property or death badly needs to be server verified, or at least a random sample of it does. You could server verify 5% of explosions and property transfers and catch 99% of the cheats while having 99% of the total traffic peer to peer and putting very little load on servers.
I would absolutely put in a basic public/private key signing system for packet data, this could remove most of the exploits. You could use the cheapest algorithm and small keys and it would introduce very little load. Networking is already in another thread client-side (game is heavily multi-threaded) and there isn't enough traffic for this to be a serious issue for CPU overhead. You only need a tiny minority of packets to be to/from servers so this would impose a minimal cost to R* and could fix the game's (richly deserved) bad reputation.
At the moment my client accepts packets affecting my position and even property from other clients, and that's completely unnecessary. In fact it's completely insane. Teleports should be triggered by my client accepting, which can always be a yes/no prompt in the client, and any packet affecting my property should come from the bank server and be signed by that server's private key. Freemode is a mess without this. From the sessions I connect to, anything with 20+ players is almost guaranteed to have a cheat in it, usually several, and these de-stabilise the session, whether by murdering everyone, locking everyone in place, putting cages over computers etc or just generally causing the game to fuck up and/or crash. I have observed basically a 1:1 ratio of cheats being active in a session and that session becoming unstable. Sessions with a handful of people or even lots of people but no cheating can be stable for 10+ hours, while sessions with an active cheater have half-lives in the minutes.
Which brings me to the griefing. Holy crap this game is terrible for griefing. By FAR the most toxic community I've ever encountered. There are a LOT of great players in the game but any lobby of 20+ has at least one total a-hole in it whose joy comes solely from screwing up other players' play sessions. There is a huge overlap between griefers and cheats, for one thing, so fixing one would do a LOT toward resolving the other. I would say a majority of the non-consenting PVP I've been hit with, I find that my opponent either has unbelievably excellent aim (like the sniper shot through the tiny window of my speeding armoured car they can mysteriously repeat 7 times) or they're invulnerable, taking several grenade direct hits or a bunch of sticky bombs without dying etc.
All too often when these players can't get their joy from making others suffer with PVP, they resort to cheats that make everyone explode remotely, lock everyone in place, put cages on terminals etc or just crash the session. Fixing the cheating would go a long way toward fixing the griefing too.
I think the other big fix would be the new user experience and the progression system. I feel a huge amount of resentment from griefer players. They seem to be people who like the game but can't figure out how to make money, so they buy shark cards and buy the oppressor II (which, by the way should be nerfed, or removed, or an effective/accessible counter be added) and just grief people.
With missions and heists being the way they are, it's easy to see how players feel trapped by in-game poverty and respond in this way. The game for them becomes punishing players who are more successful and working through their feelings of resentment and jealousy that way.
I think updates to the mission system to make it less repetitive (easy since there's hundreds of good ones) and a few fixes to heists would achieve this. Heists are very lucrative if you can figure them out.
Basically, the community is SO toxic and the game SO unstable in Freemode that I would absolutely have permanently quit on day one or two, had it not been for the fact that I went into the game with friends.
We're able to operate our own 2-4 person heist crew and that lets us bypass some of the worst Freemode douchebaggery and make money. Now I can do Cayo, I don't bother with the awful MC club businesses (SO many players love to disrupt these) and most of my Freemode time is restricted to Nightclub stuff, and setups for Cayo.
Freemode is, however, so unstable that that Cayo setups fail about 30-50% of the time. Correlation with cheaters being active in Freemode and the setups failing is very, very strong. In fact, when I find myself in a quiet session I make myself do the Cayo setups whether I feel like it or not because doing so saves a ton of time re-starting failed/bugged out ones.
So, to sum up, brilliant game buried under an absolute fountain of boiling hot dogshit in the form of a mega toxic community and cheating so rife it's beyond a joke. I've got a standing thumbs-down review on Steam for this game for those reasons. I don't imagine R* are ever going to fix it, given that it's had these problems since launch and it's now 7 (?) years old, but that's what I think.

This is mostly written in the GTA Online perspective, though it has crossover into RDR Online as well.
To bring everyone up to speed on network topology in games:
GTA Online uses what's called a peer-to-peer mesh network setup. This means that every PC/console on a connected session is talking to every other PC/console in that session. The preferred alternative for most multiplayer games is sever-client, where in every PC/console is talking with a single server.
With p2p mesh, this means that everyone shares authority. What this translates to is that a server is not the single authority checking for malicious activity, much of which anyone who has played GTA Online for is familiar with. This also means that anyone with the know-how can figure out what IP every other person is connecting from. This can lead to other malicious activity outside of the game.
But standing up dedicated servers costs money. Why not avoid that?
There are plenty of cases to be made where peer-to-peer connectivity makes sense, especially from a cost-savings perspective. But in some cases, like GTA Online, the benefits/gains from using a server-client setup far outweigh the costs.
So, in no particular order:

What Dedicated Servers Would Have Brought to RS/T2:

More purchases of cash in the Social store.
We'll start with the obvious here. When someone can get into a game and ask about [redacted method of obtaining money/goods/vehicles/XP] and get a response 50% of the time, it's an obvious miss on being able to purchase prepaid in-game credit cards from the store. There's no incentive. And if they don't want to ask someone to do it, they can do it themselves.
Nevermind that the same group of people who can [redacted method of obtaining money/goods/vehicles/XP] will also just grief sessions. Better yet:
Better Control on Hackers/Modders
Anyone who is on the outside of RDR2 or GTA multiplayer has probably only heard telltale of what modders do in these games. Here's a list of what I've personally experienced:

• Crash game sessions for individuals or the whole lobby
• Send text messages as players in a session
• Cycle the daytime so frequently that it can cause seizures
• Blow up and kill all players instantly in a session
• Join sessions regardless of session privacy settings (friends only, solo, crew only, invite only)
  • This is done by finding a unique identifier in Rockstar online. I don't know the details; that's how a modder described it to me.
  • This is especially impactful to anyone who streams, as they only need to see their in-game name and do the aforementioned to join their session and hold it hostage/ruin it. Getting rid of this yields more, is written about later.
• Grab other players and teleport them around the map
• Attach objects to players so they can't get anywhere
• Cage players
• Generate endless in-game currency (which is something Rockstar offers as purchasable in their store).

The list goes on. The biggest reason for using dedicated servers, honestly, is to get rid of the griefers. It's enough so that I've seen people ask if someone is running a specific type of mod, and they know the commands to use to get gifted vehicles, cash, etc. It's prolific and horrible.
But cleaning those things up and preventing them means:
Higher volume of Twitch streamers.
It seems easily correlated, but Twitch's research shows that livestreaming leads to better game sales. The reason this isn't streamed as broadly is because not everyone can get enough reliable people for a heist. Private sessions can be invaded by the same people who also [redacted method of obtaining money]. This is regardless of the privacy of a lobby, because those same people can find a unique identifier on the public Rockstar social site and join it, regardless of whether or not they're a friend or a crew member-- or simply not invited.
What this translates to are people who have such a low bar to pass to join a streamer's game and hold the experience hostage, crash the session or do any other number of malicious things. They can also impersonate people and send messages as them. So this further leads to things like not being able to do:
Twitch Rivals streams between competing streamer teams.
Imagine this: the game is pretty solidly protected from people who [redacted method of obtaining money] and those incidents they generate are rare, and when they do pop up, they're punished. So, streaming this game is far more viable. Competitive crews start forming, and Rockstar promotes an event with streamers where they're able to host lobbies and get 24, 36 or even 48 streamers in one session running 12 different crews for things like:

• Business goods battles
• Arena wars
• Deathmatches
• Races

And so on and so forth. But because items have to be obtained through legitimate game mechanics, it also implements a grind. Maybe these groups/crews have been running for a while. But then you'd also be able to do:
Streamer Drops through Connected Accounts
We've seen other games do this, where viewers can get "drops" into their game by watching the streamer play it. These drops could have been literally anything that was on the Diamond Casino Wheel of Fortune. It could have even been a bonus spin at the wheel, to encourage getting the player in the game.
The Long-Term, Sharded MMO Experience
This translates to cash because people would be continually playing the game, which means more people paying for in-game cash and general popularity because more people would be streaming it, but this is the bigger buyback to the player, too.
Imagine a crew that worked hard at completing a certain set of heists on hard difficulty, no deaths, consecutive. Four people who are streaming their attempt like people do for raid bosses. And their reward was a unique yacht only available for that achievement.
A ranked arena war system that awarded players who got 100 wins with a unique vehicle or livery.
The system could have been adjusted to make some things a grind. Making that money with friends, and then knowing that if someone had a high-end apartment, much less a casino penthouse, that they earned it through blood, sweat and hard work.
Powerful crews that were running around and happen to land on the same lobby and an all-out war with tactics, reinforcements and a consideration of cash drain to get the win in Los Santos.
These are the things that Rockstar and Take2 missed out on by not having dedicated servers with protections against [redacted method of obtaining money]. They were on the verge of greatness. They were this close. And I know that a lot of this translates over for Red Dead Online, too.

Is It Too Late to Do All of This?

No, I don't think so. If RockstaTake2 were to seek redemption from this, here's what they'd have to do:
Implement a dedicated server gamemode, and only allow characters created for this game mode specifically.
If people want to continue messing around in peer-to-peer sessions, maybe they allow that for a time before slowly forcing people over (because it's all about that money, right?). But create a new character (or duplicate the looks of one), and make it only available for play on controlled, dedicated servers.
You can even put Ye Olde GTA 5 spin on it and have Lester come in and say, "Yeah, I know the simulation was pretty fucked, right? It got hacked by kids on Christmas break. But anyway, now that you know what's possible out there in this stupid, god-forsaken world, well... uh, perhaps it's time we started making some money. And you remember Fleeca, right?"
Then people start off fresh, and work on earning things through the grind. I promise you, that'll net you some untold money and viewership. And I have faith enough that even if you made a very solid push into authoritative client-host conversion from peer-to-peer mesh, allowing the authoritative client-host to be controlled by Rockstar servers, you'd get something out of it.
And I will put a disclaimer on here: I don't know if the game engine is so archaic that it wouldn't allow for this kind of change. And if that is indeed the case, then the only thing that I can say is you missed out on all of the above by choosing to design what you did, because it is a proprietary engine.
But if you can, imaginary Rockstar or Take2 directory reading this, please, I implore you. Push for the change. This has been one of the best social games for me during lockdown, and I can't overstate how much everyone will benefit from this.
Sincerely,
~The Village Idiot

I'm pretty happy they finally took care of us people too afraid or scarred by previous relationships to have consecutive friends a chance to finally heist.
The Diamond Casino heist was alright but i never had friends who played with me more than once as that mother had a steep learning curve so i was never that eager to wade through it more than a couple times.
Regular heists? Forget about it.
Would you believe the only time i have ever been successful on any heist was the Prison Break level and I was the pilot and we finished on the first time? This was my first playthrough, setups and all, on my first time ever trying these heists. Wasn't my heist. No progress saved.
But this heist...
No friends..
No public lobbies...
Made by Rockstar employees from home...
They really did finally understand loneliness when they were stuck at home, making their new heist during their summer lobby droppathon.
Not all of us have great internet (I sometimes do) or friends (eh, kinda... i blew them up a couple of times [literally in self defense, I'm a very playful and defensive player] and now they switch lobbies. Also, every person i friend gets virally and hate speech level toxic when I don't regularly play [there's another couple stories about that too but I think we've rabbit trailed enough]).
Anyways,
Thanks for thinking of us lovely players too.
FIX THE SUB HELICOPTER MENU GLITCH WHEN YOU HAVE THE TIME.
Amazing update though, truly my absolute favorite of them all and I'm saying that with full sincerity. Fucking brilliant. If you accidentally buff the explosion radius of the submarine missile by 2x but slow the recharge to 5 minutes or maybe 10 minutes a console, I would completely understand and, in fact, encourage it. Tired a couple connections to public lobbies and, I mean, for the love of God... it's Red Dawn, Freedom Fighters, Command & Conquer Red Alert 3, Jesus Missile Mother Fucking Christ...
But private is just chugging along quite nicely and now i can finally play this wonderful game like I've heard others do.
I refuse to cheat
I refuse to glitch
I refuse to dupe
I've purchased shark cards ONLY ONCE (megladon, ugh...)
And jee wiz
IT'S TAKEN FOREVER TO GET HERE
But here I am, Finally enjoying my wonderful toys that get swatted out of the air by flying murder bikes.
To do
Setup missions! YAY! B11 FINALLY HAS PURPOSE!
Fucking brilliant! Thank you!
Heard you can use missiles to do setups but I did one mission of Headhunter where it took to the last minute and i only missed once. Wow! Breather! Maybe, don't nerf the missiles during missions? That Ruiner mission kinda law? But I digress again..
Thankyouthankyouigotkilledduringaheistbyatreethankyouthankyouthankyou
I promise I'll buy a small shark card, as a thank you, for this wonderful update. I'm not fucking Amazon McBaldystock so I'm thinking a ten'r maybe? That'd cool? Ok then.
Make more of this.
And nerf the public Russian invasion, In a month or so...
heheheheheheOWhehehe

I have written this for people who are starting with 0 GTA$ and making their way into gta online.
So if you don't have a high end apartment, a bunker, a clubhouse or anything like that this method will make you earn a good amount of money to start buying some important things in gta online.
First of all, the most important thing is that forget investing money into a good looking house or a good looking car. You don't need those right now.

Before you read:-

These methods have been tested by me and I now have 5,000,000 GTA$ in my maze bank account right now. However, it takes time. A lot of time. It may even take a month for you to reach this million dollar mark. However, this early hard work can pay off really well in future. And you soon might be making 100,000 GTA$ every day.

Before you start making money, do this:-

An easy way to make your gta online experience better is by playing solo. You can either play solo session or a private public session. The solo session is the easiest way but later it might have restrictions. A private public session can be achieved by tweaking some settings which are different for pc and console. Invite only session can also be considered as an alternate for solo session.
A public lobby may have hackers which can ruin your early experience of the game. Public session may even have high level players that can cause chaos or can try to kill you. I had some difficulties trying to play gta online for the first time with players killing me in a public lobby.

More is better:-

Before you start making money, it is always great to have a friend. It is not necessary but is always better. If you have a friend, you both can play in an invite only session and can play missions together (you both will earn the same).
Also, some missions may require minimum of 2 players. So depending on a stranger may be difficult due to no communication. So if you have a friend playing with you, it is always great.

Starters:-

A vehicle:-
Something wrong many new players do is that they try to invest money in more vehicles. I see people who show off their garage full of cars but didn't spend any money of profitable businesses. You need to know that buying more vehicles is not going to earn money. You just need 1 fast car, and you are ok to get started.
So you need a 'fast' car. For new players, the Elegy RH8 works super great. It is faster than most other cars and is ABSOLUTELY FREE.
To get this free car, just link your social club account with gta online and you have the car.
Alternate method:-
If you don't have a social club account or you don't want to link it. You can just find a decent car in the game and steal it. From there, just go to Los Santos Customs and make it yours by paying some money.
You can store it in your garage anytime.
But make sure the car you choose is fast. These cars are not that fast but will for a new player these are great
A garage:-
Where will you store you car? A garage. When you have just 1 car, you don't need to buy a 10 car garage or a 6 car garage. You just need a 2 car garage that is available on the Dynasty8 website for 25,000 GTA$.
Now if you don't have that money, don't worry. Just keep reading and you'll get that money soon.

Early money:-

Contact missions:-
These are one of the most easy way is to contact characters to earn money.
Basically, characters such as Lamar, Lester, Gerald, etc. will give you missions and tasks which you have to complete and you will be payed for each mission. Some missions may be easy whereas some may be difficult. Again, if you have a friend playing with you, missions can be completed faster and much easily.
Some characters may get unlocked later on in the game but I got my first 100,000 GTA$ by doing Lamar missions. Then you can do some Gerald, Lester, Trevor, etc. missions.
The maximum pay each mission gives is around 16000 - 19000 GTA$ when done at hard difficulty with no mistakes. To based on calculations, by doing 10 such missions, you get 160000 GTA$ minimum that is super great. And there are more than 60 such missions all over gta online.
And if you keep doing other contact missions, you will soon get enough money to buy a decent high end apartment.
Treasure hunt:-
Treasure hunt is the easiest way to earn 200000 - 250000 GTA$. But these are pretty time consuming and tricky. You will get a treasure hunt email at any random time and by collecting all clues, you will be given a revolver. Then do a special task with that particular revolver, and you will earn 200000 - 250000 GTA$ depending upon the task.
The task may be like 'get 50 headshots with the revolver'.
There are walkthroughs of each treasure hunt available. Just google them or search them on youtube.
There are many treasure hunts available but they don't come very fast. You'll have to wait for the email to come and then start the treasure hunt.
Doing all treasure hunts can give you minimum of 500000 GTA$. However, they can take a lot of time.
Spin the lucky wheel everyday:-
The casino has a lucky wheel. And you can get many things from it. You can win a car, clothing or casino chips. You can rotate the wheel once per day.
It is super great if you are lucky enough. The highest prize is a car.
Then comes 50000 or 25000 chips. If you get chips you can either use them in casino games, or you can convert it into money.
Which means, 1 chip = 1 GTA$ and 50000 chips = 50000 GTA$
You also get 1000 chips once every day for free.
Flight school:-
There is a flight school in the Los Santos international airport. There are challenges you have to do in an airplane. Do all of them and complete them at gold medal.
This will give you 240000 GTA$.
Plus, it's free and you will improve your flying skills

When do you earn a million ?

It will take time and skill. There are many ways you earn a million. And they take time and investment. So here are the 2 easiest ways to earn a million that take less investment.
Facility:-
Once you have around 650000 GTA$ you can buy a facility from the maze Bank foreclosures website. The cheapest one is available for 650000 GTA$. From there you can start doing the Doomsday heist and unlock other heists as well. There are 3 acts which you have to do.
The problem ?
It requires investment and friends (not really).
So each heist requires the leader to invest into equipments. You may even need to spend more than 70000 GTA$ for each heist setup. You may even need a good fast and armoured car for better heist.
Then each heist requires 4 people. It is not necessary these 3 people are your friends. You can invite other players in the session to the heist. But many times those people can mess up or you may not even find any person to join the heist.
After all heists, I bet you may be a millionaire or close.
High end apartment:-
This is pretty easy. The cheapest high end apartment is less than 500000 GTA$. Probably 300000 GTA$. Just buy a high end apartment (Weazel plaza, Richards magestic or 3 Alta st.) and you can unlock the heist room. From there you can do heists such as Fleeca job or Pacific job and earn good money.
Again, you need 3 more people.
Positive point, the investment here is lesser than the facility but the pay is also less.

That's it.

After this, you are no longer a beginner

and you can go ahead and buy a bunker or an office. Then become a CEO/VIP and unlock new missions.
If you think i missed something, comment down.
I hope it helped.

Edits:-

u/leekshooter suggested not to do Doomsday Heist for a new player as it may be difficult. You may not have sufficient equipments for the heist when doing Act 3. So make sure you consider the difficulty level if you are new to heists.
Make sure to read the comment of u/braggs0815 as they have suggested a profitable method of earning money with vip jobs and later in the game investing on facility.