you can setup multiple sites using the same content with awiz, the content resides in one spot but all sites can be built to look differently. Or you can setup a common unbranded members area, or better yet, use php includes to setup a header and then pull in the common php code for the main part of the site's pages. Or if you want to be lazy about it, setup a totally separate domain and alias members.domain1.com, members.domain2.com, etc, and have your ccbill scripts post userids/passwords to the same single .htpasswd file.

there are prolly another 50 ways to do this too, like use frames or use gateway entry pages plus strongbox to jump to the common site, or setup a megasite and have all paysites back onto it...want me to keep going?