Once you have your template setup you may want to setup a special area for users to login. This is not an easy item to add and we do not provide support for setting the following scripts up, however, we have provided these links to give you some ideas about what can be setup.
I looked at 3 different membership scripts: Membershipclientpro.com - This one looked complete, but their site didn't really tell you anything on a technical level. They also really don't say much about who they are. Easymemberpro.com - Same as above.
Amemberpro.com - I chose these guys to use at Reallylearnguitar.com. Lots of technical info in their on-line user guide, great info and responses on their discussion board, they installed it for free to my server and configured it to my specs that I provided. Takes about 24 hours for turnaround to get a response, but they definitely do get back to you and they are helpful. They did all the difficult setup like setting up the CRON jobs. You receive a 3 month license key that they make permanent after they're sure you're not going to cancel your credit card payment. All of these are probably ok to post for your customers. All offer the cool feature of letting you manage an affiliate program. aMember Pro seems to have compatibility with many more payment processing provider options. They can also pay your affiliates in your program via PayPal Masspay.