I will give you my experience, as it was a good one, and I am very pleased with the outcome.
I found the aircraft listed for sale and so I made contact with the seller. Many people are happy to deal over email and text, whereas I prefer to talk, so I called and we had a chat. It's also a good way to gauge people when you talk to them. Anyways, we negotiated a price and once we agreed we also agreed to have the aircraft independently inspected by a LAME to ensure the bird was as described.
Part of the negotiation was that I would pay the inspection, as long as the aircraft come back in A1, as the owner suspected it would. (and it did)! Once that was done, a substantial deposit was paid, and the balance would be paid once I arrived and inspected the aircraft personally.
I flew myself and my buddy (a CFI) up to the aircraft where he and I inspected the machine again, from top to bottom. We went over the entire plane, the paperwork, had a chat to the owner etc etc. My CFI mate then took it for a fly, and reported back all was good.
We settled the monies and signed papers etc, and with a smile and handshake, we departed and spent the next 2 days flying her home. All the way home I got to experience the sounds and feel of my aircraft knowing I had a very experienced pilot sitting beside me. It was very reassuring, but it also meant I clocked 13 hours in my aircraft to get a really good feel for her.
So.. what did I take away from this....
Talk to the owner - and get a feel. If I was not happy with what I was hearing, I would look for another machine.
Get it inspected by a LAME and get the full report sent to you BEFORE you hand over any serious cash
Go and pick the machine up yourself and go over the entire thing. Discuss any concerns with the owner etc, and get him to show you anything that he feels you should know.
lastly - if something does not feel right - walk away! Don't get emotionally attached to it before you even see it. Keep it in mind that you may not come home with it.
I was quite happy to fly back on the QANTAS jet if it did not work out. I was very happy that the current owner was a nice guy, and everything was as he said it was. So... Happy result in the end.
Cheers
J