Your not asking for much are ya?
What your looking for then is a restored Z or one thats been in storage forever. If you can find a 240Z with a good drivetrain(no leaks and runs perfect), has a none cracked dash, and the body is rust free.......then your probably not going to be in the area that I would call a cheap car. If you were looking for a 280Z you might be able to get what you want cheap but I doubt your going to get a 240Z in that kind of condition cheap. I would say be prepaired to spend $3500+ easy. The rust free part is the part that will really make the value of the car go up!
What kind of price range are you in?
Guy