Affiliate software/plugin - Accessible to program members on our site/subdomain.

Starting an affiliate program to track closed business and pay referrers. Would like to set this up as a subdomain on my primary URL. I'm running WordPress and was thinking about using something like this: [login to view URL] I am capable of managing settings and content once the script were functional. I need assistance with: -any PHP coding -any SQL integration Free to answer additional questions. This is my first post. Hope this is not too vague.