My problem...well, one of my many problems with eBay/Paypal is that it's set up so that the bad guy wins. A bad buyer can pay with a credit card, file a chargeback and get the item and their money back very easily. A bad seller can quickly withdraw the money that you send them, ignore their eBay/Paypal account and Paypal just says, "Sorry!" I've been screwed both ways.
Assuming you're not getting scammed...well, unless you're buying from someone who knows pins (a re-seller, retailer, heathen) you have no idea how much that person who spent 10 minutes to sell a $5k item knows about their pin. Home use usually means home use since they bought it 2 years ago (the 10 years before that it was in a wet storage locker). Very nice can mean anything from it's one of the nicest that they've seen out of 10+ examples or the flippers work, it kicks out a ball and the cabinet still stands (with 10 drywall screws holding it together).
I'd like to think that you can still find good machines on eBay though. I sell there all the time I just decided to warranty the boards now because anytime a board issue arose (usually from shipping) I would just have them send it back for me to fix for free. But for all that I explain and offer, most buyers just look at the price and the pictures. The more possibly negative things I show or describe, the more likely they are to hit the back button and buy one from someone who shows 1 picture and a single line saying "very nice condition" in the description. Then they find me again later and ask for help.
I guess the bottom line would be, know who you're dealing with first, and then find out what you're getting.