I just found a video on membership sites that gives a good background on how to start a paid membership site.
Easy Membership Sites reveals the 4 keys to a paid membership site.
Take a look.
James Maduk is the founder of WPBlogSupport.com as well as the author of the 62 Best Selling "Secrets My Mom Never Told Me About Internet Marketing" ebooks. James also runs WPGrow.com a WordPress Campus with Courses, Workshops and Certification for WordPress Bloggers who want to Start, Build and Grow there WordPress Powered business online.