First Step: Click continue career (if you have an account)
Second Step: Go to code entry
Third Step: Type in unlockallthings (if you allready have and it wont let you then listen)
Forth Step: Sell all the cars you unlock from the code (not the ones you won)
Fith Step: Go Back to the main screen and turn off the PS2 and do everything again from First Step.

If you follow all those steps correctly than you should earn ALOT! of money!