Give all your money to the desired character. Go to roulette ($5,000 or more). Select the three CPU characters and let them all bet $5,000 on any number. Have your character bet $0.
Hidden slot machine:
Repeatedly select the following options in order on the tool bar in the lower right corner: "Games", "Slots", "Progressive", "$100 dollar machine". Eventually, a progressive slot machine with an "Out of Order" will appear. Play this machine to get a bigger pay out than the other slot machines.