Any tips on how to build affiliates for your website? Specifically, membership sites. The cost for access to the website is a one-time fee of $15 but most of the members elect to participate in a survey which will reduce their cost to $10. Should I offer $5 for an affiliate as well?

Yes you will have to give incentives to affiliates plus you will have to reach to them. Giving examples of existing earning affiliates can attract as well.