No one can give you a definitive answer about a particular transaction.
First thing to do is to look at the seller's profile here. If they have a long history its likely they are an honorable audio enthusiast like you.
You can also contact the seller and ask if they have feedback as a seller on another site like Audiogon or Ebay. Then check that feedback.
Using PayPal, as you mentioned, provides a safeguard.
I've bought used gear on Audiogon and Ebay without issue. Never bought here.
Also depends upon what you are buying, how difficult it is to ship, the location of the seller, etc., etc.
Always a judgement call and always more risky than buying new from an authorized dealer.
Since its a judgement call only you can make that decision once you check things out.
Don't forget that the seller will want to check you out, too. Nothing worse for a seller than a transaction gone bad. I know.
Remember that the seller is taking a risk, too.