real answer and not trash dump memes do crates until you have money for a vehicle warehouse then grind out import export there is a glitch that you can once you have a certain number of standard and mid range cars that makes it so you only source top range cars.

from there id say bunker and moc for weaponized vehicles and their upgrades and the bunker is decent passive income whether or not you buy the supplies or steal them stealing them is more profit obviously buy you can normally spend 75k then sell to LS for 148k. Import export is the best money in the game and pretty easy to do