Add $1 to Career Earnings
Select the "Options" menu and go to the "Cheats" submenu. Enter "kubmir" into the text box and press the "R2" button to set this cheat to the top slot on the menu. If you have a controller with the auto-fire feature, simply tape the "R2" and "X" buttons down simultaneously and the money will continue to increase until the tape is removed. If you do not have the auto-fire feature, hold down the same combination of buttons for as long as you want to continue increasing your money. By holding down the "R2" and "X" buttons, you will quickly increase the money in your career earnings and can use the additional money to buy new vehicles or upgrades for your current ones.
Easy Money
In career mode, buy any car and fix it up nicely with Level 2 performance parts and as many upgrades as you possibly can. The value of the car will increase exponentially. Go to the "Manage Vehicle" menu and make duplicates of the vehicle. When making duplicates, be sure to change at least some of the characters of the VIN number. Go to the "Sell Vehicle" option on the car menu and sell all of the duplicates of your vehicle for easy money.
Unlock Lamborghini Murcielago
Win the U.S. Champ Series on any difficulty level to unlock the Lamborghini Murcielago. Go to the "Sell Vehicle" option on the car menu and sell the car for quick cash. This vehicle is the most expensive in the game, coming in with a price tag of over $250,000.