Help with membership site script.

Hi, I am sure I am breaking all the rules posting this before I say hi, so, HI

My name is Earle and here is my question/dilemma.
I need a scripting solution for a membership/affiliate site. Here are the bones of what I want it to do.

1. Be hosted on my own hosting with control of the main page content.
2. Accept paypal and alertpay as payment processors with the person being directed to the site setup/content/etc. when completed.
3. An affiliate/program page with a number of different programs on it- for example, ppc programs like clixsense, neobux. other affiliate programs, hosting, or content to be added later. I would like the person signing up to be able to add their own links somewhere and then get their own page with the links changed and their referrer or username in the URL- for example,
myaffliatesitedotcom/someuser or the php equivalent- ?rsomeuser

If possible, I would also like the person to be able to choose to replicate the whole site on their own hosting if they wanted to.

I don't really need the site to have a recurring monthly, just an initial buy.

I know this kind of script is out there, but I am not sure where to look first and what I should be expecting to pay to get it.

Thanks a bunch in advance for any help with this. I really appreciate it.

One tired teacher in Houston. Earle