I've purchased 2 vintage machines and a PQ1500s off Ebay. In each case I did a lot of checking into the seller. I made sure they had rating of at least 98% and lots of reviews as a seller. I also checked out the written reviews to see how what buyers had to say about the items they received. And, I paid with Paypal. eBay has a lot of safety features in place to help protect the buyer from bad sellers, but they do sometimes get through. If you do have a bad experience on eBay there are mechanisms in place to help you get your money back.
Rob