Welcome to AC!
I've bought and sold from the Trading Circle, its free but there is no protection. Everything is done on a handshake, so best to know the seller/buyer. I will say I've had nothing but good experiences. Even a recent purchase of a DAC that didn't work with my computer was returned for a refund (and is still for sale).
Sales of gear not sold by AC vendors or discussed here go much slower than on Audiogon. (Don't use their insurance - it's a mess as per recent AC thread.)