ive never done anything other than log on to online games and play so theres not much I can do about it if random money appears so im not worried about any possible bans for cheating.
to be honest I don't even play the story or do many missions online. I just log on to play with my kids when theyre home and generally arse about in deathmatches with other online players. having all that cash though has pretty much killed the little interest I had in the game though as theres no real point now. it doesn't matter what happens during gameplay when you've got enough cash to buy or replace anything that gets destroyed.
the majority of my gaming time is still spent in team deathmatches on call of duty where im a legitimate prestige master with a k/d ratio of 1.64 and about 51000 kills...