I can imagine someone suing over a misunderstanding because of an X/Y problem. Person A asks a really obtuse programming question, Person B answers it literally, and then Person A goes on to use Person B's answer to build a nuclear reactor controlled by a raspi. Person B then gets sued by Person A when it melts down.
Obviously that is a bit of an exaggeration, but it isn't hard to imagine a point in the future where programmers will be held to the same standards as certified professionals such as lawyers, doctors, and engineers. While it's really unlikely any particular programmer will be sued over advice they gave online, it would really horrible to be the person that someone chose to make an example of.
No random Craigslist clown is coming into the house where my wife sleeps, even if I escorted them in with a gun to their head because they could scope it out and come back later. I said I'd record a video of it working and send that over. No more replies. :)
Worst case, I would probably have it in the garage and they can look at it there. Probably a risk you have to take to have someone cart off a big old treadmill.
One thing I would definitely do is probably sell it fairly cheap. Just to make sure it moves with the 1st person who is interested. Rather than get a bunch of time online and gazers coming over. People are also less likely to complain about something if they get a deal on it too so it's a win/win. Well other than the cash lost but I'd make that deal.
[0]http://www.tractorsupply.com/tsc/product/carry-on-trailer-me...
One other thought is to use a more localized service like Nextdoor where you are only selling to people in your subdivision/neighborhood. I would think this would cut down on the riff raff, but also cuts down on potential buyers.