There is a way to get really easy money in Bioshock 2 for the PS3, Xbox 360, and PC.
All you need to do is find any working slot machine in the game. Save your game before you start playing. Spin it a few times, and if you lose several times in a row, simply reload your saved game and try again. If you win money, save your game. Wash, rinse, repeat, and you can get a ton of money in a few minutes of playing.
