Keep in mind that the RPGFan staff has no control over what is bought and sold here, and as such we are in no way responsible if a transaction goes bad. If someone refuses to pay or refuses to send you what you paid for, no one associated with this site can or will aid you in solving your problem.
Linking to any online auctions you may have going on at the moment is not only allowed, but encouraged. A third party such as eBay provides a greater amount of fraud prevention than any direct sale or purchase ever could.
Registering on these boards just to buy or sell something is perfectly fine, but don't be surprised if people aren't willing to deal with a stranger.