I think every Marketplace has a sticky explaining the rules- which include the requisite upgraded membership (and how to get it). If not in the sticky, then in the forum description:
Originally Posted by For Sale in main Marketplace
Items for sale, bicycle and cycling related items only, please! Requires upgraded Membership to post new threads. This forum is intended for individual members to sell their bikes and bike related gear, and not for commercial ventures or company sales. Prices must be quoted up front, we are not an auction site, and do not link to your ebay auctions.
Edit: note that you also need 50 posts before you can access the PM system here, but an upgraded membership will waive that minimum post count.
Originally Posted by Cyril
Ride what and in what manner pleases you. Those that mind don't matter, and those that matter don't mind. srsly.