After launch, NPCs will appear over your head, instantly die and drop 2000 bucks each.
Grand Theft Auto 5 (GTA V): Cheat (External Ped Dropper ver. 1.0.3) [1.40] Free Download
So in just a couple of minutes you can farm huge amounts.
How to install and configure the cheat:
Start gta 5 and go to session.
Depending on the version of the game Steam or RSC, run the cheat.
Find an open and crowded place in the game, there should be no objects above you that will interfere with the farming of money.
Press “Numpad +” to speed up farming.
Press “Numpad -” to slow down.
There are 13 speeds in total (0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 10, 20, 40, 80, 320 NPCs per second)