Quoted from GoldenBeard:
A little nervous about buying ‘used’ and also from buying from someone I don’t know for a lot of money.
I'm going to echo what a lot of others have said here and try to get two machines as opposed to one expensive one.
Other than play fields falling apart on some games, Stern's are pretty well put together. I have a few Stern's I bought that were routed their entire life, have 10,000+ plays on them and I've only run into little issues here or there. As for buying used from someone you don't know, I wouldn't hesitate to make a purchase (in person). Take a friend along that knows pinball machines to look things over for you before you buy. If you have any issues down the road with the machine, there are a lot of really nice people in this community that would be more than happy to help.
My first machine was used and I didn't even know how to remove the glass. The seller, who has since become a good friend of mine, showed me everything I needed to know and offered to help if there was ever a problem.