remove affiliate sign-up from membership

I have Affiliates and Membership on a site that is selling 3 different membership packages. I do not like that the affiliates have to see all the paid membership options when they register – I want someone totally uninterested in signing up for a paid package to have a fast and easy way to become and affiliate. How can I streamline this?

Right now I have affiliate as a level of membership and the free user level as that in the membership options.

Please tell me a better way?