I agree completely. THey may want to get rid of a boat anchor, but may decide to keep something that runs.
Also, one time a friend of mine went to look at an old Lincoln. He tried to get it running, and it backfired and caught fire. They got it out quickly, but it left some marks, and the owner was really pissed. Threatened to sue my friend for damaging the car.
If you want to try to get it running there, dont do it until the paperwork is done, and in your hand. Then, you can do whatever you want with YOUR new car.