when you're playing much of the story, armoured cars and smuggling missions are a pretty good way... (you probably know this; i'm just making conversation). armored car heists are about $10,000 and once you kinda know where the spawn, it's easy to get an extra 1-2 between most missions.two smuggling missions take maybe 6-7 minutes and get you about the same, too. i mean, they're not very helpful for the end-game... no buying the golf course like that. but at least for the first 50-75% of the game, it's a nice little way to compliment your mods, a few cars from the internet, etc
but yeah, the end-game money is massively broken, you basically have to either use a bug, exploit multiple save files on Bawsaq stocks, abuse the ASSN missions, or some other unnatural and cheesy thing
but i think the game is more fun when you're poor and struggling to afford mods, and every armoured car is like Christmas Day....
it's one reason I chose not to end up using the new stock bug. i had a 100% file on PS3 with everyone at $2B and my reaction to it was like... ok, now what
. as Michael says during Marriage Counseling, when you get rich, the first thing you lose is the fire!