Well its sorta hard 2.
1.) Buy a CHEAP car.
2.) DO NOT UPGRADE IT.
3.) Enter races with it and WIN AT ALL COST.
the sell value will go up if u win with it, but it goes down after u sell it.
also, THERE ARE NO CHEATS YET. im findig out how to get them from inside the game, or i will contact the makers. so tell me what to do xD.