NO. Forget what you have seen CW. - think more about your own site having one extra page dedicated to classifieds adverts for say 'leather goods' , with a dedicated classified adverts directory pointing at your niche classifieds page. Then imagine my users directed selected adverts towards that page
Your page - your content .
In return your site offers your users a simple submit form for any item they wish to list or any item they need to buy . . Where it is whisked away directly to the webmaster that wants it.