If you know more ways list them in this thread.
Go to special condition races, go to the second race called Capri Rally (Easy), race both tracks, and you will win a Toyota Rally car, you can sell it for $265000. Then, go back to the Capri Rally, and enter. It will ask you if you want to clear race data, choose okay, race the races again... and you'll win the Toyota Rally car again..and you can sell it again for $265000. Easy way to get alot of cash quick.