Complete Missions And Jobs
Missions are automatic jobs handed to you solo (or with other players). When you enter GTA Online, Lamar (from the single-player campaign) will help your character get set up. Completing these missions will earn you cash early on and help you purchase some much-needed elements. Be sure to check your phone for texts or calls and answer them. The key here is to stay busy and apply yourself.
Rob Convenient Stores
If you want to wrack up dough quickly, the absolute best way to earn money at the start is by robbing convenient stores. It's the quickest and usually the easiest way to accumulate a ton of currency. There are 18 stores in GTA Online, and they're all marked on your map. There's always a catch, though. Some stores require two players. In this case, get someone you can trust (a friend, girlfriend or your brother) and enter one. If you aren't aware of the other player's intentions, don't risk it; chances are they'll rob you.
Once you enter a store, equip your weapon and hold the cashier at gunpoint. At this moment, you must intimidate the cashier and convince him/her to give you the money. You will see an intimidation bar on the lower-right part of the screen – fill it to receive the money. A key recommendation is to have a headset plugged in, because yelling at cashiers works smoothly and draws less cops without gunfire. With the money gathered, you'll have one more task: escape the police.
Want to make cash like a criminal? Steal ANY car, then bring it to a Los Santos Customs. Every vehicle has the option to sell from the custom menu. The price highly depends on the type of car and its condition, so make repairs before selling it.
Click here to learn even more ways to make cash in GTA 5.