Selling a running motor.

I currently have a running 383 727 for sale that is in my Dart. I've decided to go another route. I have an interested party that says he's coming from a long distance. Do you guys think it's unreasonable to ask for half down before I pull the engine? With all the flakes out there I'd rather not pull the engine if I don't have to at the moment for someone that won't show up. What are your thoughts?