Look at S2 Member http://www.s2member.com/
The s2Member® Framework is an extremely versatile & powerful (free) membership management plugin for WordPress®. The s2Member® Framework plugin integrates seamlessly with PayPal® Standard Buttons (very easy), and fully supports recurring billing, with the ability to track affiliate commissions on a recurring basis (through your choice of many affiliate platforms). s2Member® supports custom Pages for registration; including Custom Registration/Profile Fields, account access, and a whole lot more! See expanding features below.