Outside of going on a mindless rampage, you can't do much in GTA Online without money. You need cash to buy houses, cars, and weapons -- everything that the doctor ordered for a friendly GTA Online session. So how do you make money fast in GTA Online in order to buy all these nice things?
You can always use real money to buy GTA Online Shark Cards, but there are a lot of ways to avoid that and get money through in-game antics. Now be aware, GTA Online is a grind. So expect to drop a good amount of hours robbing banks and running heists if you want that high rise apartment.
Be aware, some of the best money-making schemes won't be available when you first start out in GTA Online. Some require a cash investment up front or won't be available until you reach a certain level and buy a specific type of property.
Get started with Contact Missions
Contact Missions, normal missions that separate you from the rest of your online server, are standard outings that give new players a chance to make a little cash when just starting out. You can access them either randomly when they pop up when playing or by looking into the jobs menu in your in-game phone. You also partner up with higher-level friends and earn more cash.
Races and time trials are also good quick and early ways to make money in GTA Online while starting out and they only take a few minutes to complete.
Do some Oceans 8-like Heists
You need to be rank 12 and own a high-end apartment to host a heist, which can be a big task when you're just starting out. You can either do some contact missions and races to rank up or you can join a friend's heist to make some good money, you don't need to own a high-rise if they do. Heists can get you up to $400,000 an hour if you're efficient enough with the Pacific Standard Heist being the most profitable. Even if you need to save up for a high-end apartment, heists are the best way to make money in GTA Online.
Check for Rockstar's Special Events
Rockstar will have special in-game events that give you double the money almost every week. Be sure to check out the GTA Online developer's official site, which can be accessed in-game as well, to see what the current promotions include.
Prove how important you are with VIP Work
You'll need to start an organization as either a VIP or a CEO in order to do VIP Work. Becoming a CEO requires an executive office from the Dynasty 8 Executive of properties on your phone. That'll cost you at least $1,000,000. There is no upfront cost to being a VIP, but you do need at least $50,000 in your bank account to register. Go to the SecuroServ menu on your phone and start an organization as either a CEO or VIP and then choose the "VIP Work" option. Then go wild in the available missions.
Gain some passive income
Whether it be from gunrunning, owning a nightclub, or running a motorcycle club, there are a ton of ways to set up passive income generators that earn you money while you do other things.
- Gunrunning - Own a bunker and start an organization as a CEO. Go to the computer inside your bunker and select the 'Resupply' option, then 'Steal Supplies' or 'Buy Supplies'. Buying supplies is more effective and less time consuming, do that and then your staff in the bunker will start manufacturing stock that you can sell via your laptop for a profit.
- Nightclubs - Once you own other businesses, like a gunrunning bunker, buy a nightclub and select the 'Warehouse Management' option on the computer there. Pick a technician and assign it a type of good. You can then sell these goods via the same computer, once your technician accrues them, for a profit.
- Motorcycle Club - You'll need to start a Motorcycle Club as the president after you own a clubhouse (the same way you would start any business) and then follow the same steps as the options above and buy and sell supplies for a profit.
There are a ton of ways to make money in GTA Online, so my advice would be to set up passive businesses like the ones here and then do something you enjoy doing with your time whether that be heists or other specific types of missions.