The eBay affiliate program provides two main benefits. First, by signing up and becoming an eBay affiliate, you immediately receive 5,000 credits for free advertisements on Microsoft's Link Exchange network. These credits can be used to help promote your site. Given current click-through rates, you can assume this bonus will drive 20-50 visitors to your web site.
eBay pays $3 for each visitor you refer to their site who registers
Commission checks are issued monthly once $25 in commissions have been accrued.
http://affiliates.ebay.com/