In gran turismo 5 where do i buy standard cars and how?

I noticed there is cars i really like that are standard but when i go to the dealership none of them are there all just premium. Where do i buy standard cars The car i wanna buy is the pagani zonda c12|||All the standard cars are in the used car lot I recently saw the zonda and finally got to purchase it it may take a while to find the car you want