Simple Affiliate Program

Looking for a simple affiliate program that will be installed on my server, that will allow clients to sign up as an affiliate, be given access to an admin. area where they can receive affiliate links and banners. Payments to affiliates will be through Paypal or paper check. Only looking at selling one product right now at a set price per sale for each affiliate sale. Would like to have the ability to add % of sales at a later date, but not now. Would also like to install this system on another site at a later date with simple instructions from the programmer I select.