I've successfully installed WPMU, theme and everything else seem to be working fine on subdomain. I also have the domain mapping plugin working fine. The WPMU set up is not to enable multiple blogs however. My sole reason for setting it up is simply to have a subdomain called clients.mysite.com which is for my clients only, that means that only registered users—clients, can access the site. The point of the clients. subdomain is to provide support and helpful info to my clients, and not to dispense paid-subscription content.
My question is simply: What is the best way to set it up? Site visitors will become clients after they have placed an order and prepaid for services via Paypal. I'd like them to be immediately taken to a page where they can register for a user name and password for client-area access. I've looked at a number of options (S2 Members, WP eMember, Locked Area which is a Perl CGI script) all seem to be unnecessarily complex and do not serve my simple needs exactly. Correct me if I'm wrong, my understanding is that WPMU super admin can only enable/disable registration for the entire network and not just one specific subdomain. The other simple alternative is to password protect the clients subdirectory with one password for all but that seems to be too crude and retro for my sensibilities. Currently, I am leaning towards the Locked Area Perl CGI option hesitantly, because I believe that there's got to be a simple WP plugin solution for just my needs.
Any ideas, tips and info on the subject will be much appreciated. Thanks in advance.