There is an unlimited money glitch going on right now, but the bad thing is that it is only for Xbox 360(guess not so bad if you have one).
Here is how you do it!
1: Join a Friend’s Game.
2: Then accept all his money in a Trade.
3: And Save and Quit.
4: Now, Just re-join the game and give your friend all your money.
5: Following that you must press the Xbox Guide button in the middle of your controller and then press the X button to Sign Out without saving, just make sure your friend is still in their game.
6: Last thing to do- Re-join your friend’s game once more and you’ll both have lots of money, because the game didn’t save the fact that you traded the money back to your friend. Rinse and repeat until content and wallet is phat!