I have ever car in the game available to north Americans. I bought the collectors edition which gave chromeline, stealth and gamestop cars, have all DLC even the edge camaro, and at least one of each standard and premium cars in the game, and most used ones have less than 10,000km (6200 miles). I bought those 2 new standard TVR's since it was the first time I have seen no checkmate next to a car in a while.
I am proud to say no duping or any other form of cheating, I only traded for 1 car the 370z GTA car, which I later got through a ticket anyway.
Goal now is to get 2 of every car over 1million credits, one 0/0/0 and one to race. I always try to keep around 15million in case they update the dealership with a 0km 2J or even 2D, which they never seem to do, lol. When I get close to 20 million, I buy doubles of expensive premium cars, but am quickly running out of cars to buy from 1-5 million.