LG:
OK.. Quick and dirty version. Create your member area first one or more sub dirs down from the domain root. If you can see a possibilty of more than one paysite front - it may be worth having a central content area/repository and using symbolic links. There are also several CMS's such as SiteDepth if you want to keep it simple.
Once that is done and complete - contact CCBill and any other processors and let them do the access setup (it only takes 5 mins) - then you can tailor/trim the signup/login stuff to direct members to the actual content etc.
First stage is have member content available
