Looking for an Affiliate program to process membership payments from Survey Site

I was looking into designing a survey site that would charge people an upfront membership fee to join (e.g. access the members only section). Are there any well-respected service/affiliate programs that would help me process these upfront payments I receive from my 'customers'? If this is something that could be done custom, let me know the details and any costs.

If you use Wordpress, there's Magic Members plugin and the free s2 plugin. Check it out.