The current greatest way to earn money (without farming) is to duplicate a fully upgraded car and sell it for 84-89k every hour (or more if you do the LS customs glitch)
How to duplicate.
1. Get into a friends car
2. Start a mission
3. Once mission starts you should still be in your friends car.
4. Drive into your garage.
5. Walk out of the garage.
6. Goto your mission on the phone and end it (press x)
7. When back in free mode, go into your garage and get back into your friends car
8. Drive to LS customs and sell it.
Or you can try it solo by getting into one of your cars in your garage and without driving out follow from step 2 (this depends on mission as you will sometimes spawn inside your garage which stops the car from duping)
You can also use this to get hold of cars like the sultan and once you insure it, it's yours to keep
Now that our online characters show up on the social club, let's compare how well we are all doing so far. (Add your current rank as well)
Here is mine
Global RP 193,745
Overall income $1,049,223
Overall expenses $1,020,841
Total players killed 126
Total deaths by players 71
Player vs Player Kill / Death ratio 1.774648
Distance traveled 572.01 miles
Favorite radio station Radio Los Santos
Time spent in GTA Online 1d 18h 25m 40s
Time spent in Deathmatches 0d 0h 6m 14s
Time spent in Races 0d 0h 17m 1s