During the game, you can hit Ctrl & M to raise your bankroll. This puts your cash at $5 million, no matter what your money was before. Don't use this if you have above five million or are going for a high score (as it gives you a score of 0 for cheating).

Alternately, you can go into either the CORECandidates or created character file (as described in the attribute cheat) and alter how much money you start with.