The first Autoharp I purchased, with little to no knowledge about what I was doing, I bought on eBay. When it arrived, a few of the tuning pins were loose, which meant that after all the work of tuning the Autoharp, it was out of tune in no time. A good Autoharp with tight pins should hold it's tune for quite a long time. The one I purchased later holds a tune for at least a month if not more. The seller didn't mention the loose pegs, and had I known better, I would have asked before bidding.
I ended up reselling the Autoharp, and was honest about the problem with the pins, suggesting that someone buy it that knew how to fix such things, and it ended up selling for a bit more than I paid for it. It really was a nice instrument and I'm sure someone is enjoying it right now.
A few thoughts if you're considering buying used:
* Look very carefully at the listings...are there strings missing?
* Are the tuning pins tight?
* Are there markings or scratches on the wood?
* Do you like the color of the wood?
* Are all the seams where wood joins wood secure?
* Does it come with a case and any accessories?
Ask all the questions you like, a good seller will be happy to answer them...if no answer, then move on, there are plenty of Autoharps available for sale.