I don't know how it works these days, but back when I first started collecting games, I almost exclusively bought on ebay. I recall reaching out to the sellers through a private message, asking if I could view the game before placing a bid. It worked well for a while, but eventually I moved away in favor of CL and other classifieds. I never had any issues at the time, but this was years ago when ebay was a lot younger, and prices in the hobby were actually reasonable.