After you beat the LA Street King, Karol will call you and offer you a partnership with Him. His asking price is 1 Million Dollars. Do what you have to to make a million dollars, and don't forget you can sell your car's too. After you have a Million Dollars in your Bank, Karol will contact you again. Give Him the Million Dollars. When you go back to your Garage, All Car's and All Upgrades can be purchased for ZERO Dollars. Even Car's that haven't been unlocked yet can also be purchased.