Welcome to the forum. Stick around, share your knowledge, enjoy yourself, meet some friends who share your interests, but if you wish to buy and sell, I would suggest Craig's List. We don't have a section for that, though I wish we did.
I would think a small section for the exchange of used gear, for the purpose of trading up, or helping out another hunter would promote hunting as a whole.
Problem would be to regulate it so it did not become flooded by companies hawking their wares. Maybe if it was kept strictly to used gear from members only? It is a thought.