Junkyard - unlocked on level 13. It kind of works like the barns, but the choice is much broader. On the other hand, the condition of cars and parts is most of the time very poor and the vehicles are very incomplete. The upside is that you can buy them for a song. Each visit in the junkyard generates new inventory there.
Searching junkyards for cars to renovate isn't a terrible idea. If you want to rebuild a car on new parts, you will save time on disassembling the vehicle, and money you'd otherwise have to pay for a new car (it won't cost more than couple thousand dollars). The only possible problem will be buying parts: if you don't remember all of them, you will need to constantly switch between the store and the examination screen.