Enter the "UNLOCKALLTHINGS" code. Exit to the main menu, reload Career mode, and 
you should now have the Nissan 240 SX, modern Pontiac GTO, Chevy Cobalt SS, and 
black Dodge Viper SRT 10 in your garage. Sell those four cars to get 
approximately $90,000. Then, save your career, and reset the game. Load your 
saved career. Enter the "UNLOCKALLTHINGS" code again. Exit to the main menu, 
reload Career mode, then go to your garage. The Nissan 240 SX, modern Pontiac 
GTO, Chevy Cobalt SS, and black Dodge Viper SRT 10 should be in your garage 
again. Repeat this process as much as desired.