Take into account that typical cost per click on a banner network is 25 cents you have the makings for a great return on investment. About Me Page. Many auction sites, eBay included, provide an About Me page. Again it's time to break out your list of links and point that page toward your site and talk about your business. Make sure any links out are relevant to the product you are selling.
Some auction sites prohibit any upselling or affiliate type of links inside the auction ad.
Keep in mind you get to play the part of a merchant. I think this is very valuable. You get to reverse the role and see what it is like to actually close and deliver the sale. It is not as easy as it looks. Many small businesses are ready to strike an alliance.