Inside the Nightclub on the far right (next to the door) is a terminal/TV on the wall, interact with it. It's a gambling race, if you play the arcade a few times you'll have plenty of money to spend. The race is between:
Top: Dog
Middle: Llama
Bottom: Pig
You have to keep betting llama until it wins, this is random, and it took me over 20 tries before the llama won.
If you run out of money just go to the arcade machine and win it once you'll have a ton of money.
If you missed this you can finish the game and at the main menu go to mirage and it will let you play anyways.