We make about 10-15% of our income through our affiliates. Finding good affiliates is tricky though. You need to find affiliates that have a) high traffic b) quality traffic - their customers might actually be interested in your games and c) that actually try and promote your game instead of letting it languish on some sub-page.
One incentive we have for our affiliates is a very high affiliate cut - 40%, or about $8 on a game.
In the meantime though you might be confusing affiliation with payment processing. We use BMTMicro.com to process all our payments - very simple to set up. Go and try it out for yourself