A car that came with a folding rear seat would be a good start. Definately more than a couple hinges. Im not saying its not possible to convert one over to folding seat, but its not very practical.
I found a thread on fabo about doing the conversion (with pics). Do a search on "space duster" or "space saver." You will need access to a parts car, and welding skills. I have an extra seat bottom and back, but that is the easy part.