What is a membership site?
A membership site provides information or services to those visitors who register and pay to become a member. Some membership sites bill their members on regular basis, while other have a single fee. Once someone signs up as a member, depending on the owner's set up, they are automatically billed each month. Those who sign up to become members have access to member's only information, benefits or discounts provided by the site owner on a regular basis.

Information Strategy
If you own ebooks about a certain subject there are different ways you can go about starting a members only website and making a profit from that knowledge. You can set up a blog like website where users can signup, for a fee, to receive advanced content from your website.

You can also set up an information based website where members have a set of tools to collaborate with other members around the chosen subject. This reinforces the sense of community which increases the retention.

You don't have to be a constant presence either. Simply state that you will be available X amount of times a month or week from say 12pm to 2 pm to interact with your subscribers... you get the idea. Another option that won't require a set time commitment of you is to create a forum where you can pop in and out to help members as you can.

If you are not an expert but want to learn about a particular subject, refine a certain skill or even study how to play the guitar, you can become a spoke person for people who have the same interest. Call a couple of experts in your field of interest, record keynote and make it available in your members area.

Member's Only Benefits
Offer more information of your products to members at a special price. For instance, if you have a fellow business owner who sells a product your members would find useful, ask if you can get a special deal for your members only. Most business owners will agree since there's zero upfront cost for them.

Do you offer a service or know someone who does? Again offer your members a discount created specially for them.

Affiliate Programs
Affiliate programs are another way to generate revenue from membership sites. If you promote products as an affiliate, be sure to include those promotions in emails and posts to your members. As with the previous money-making alternative, you might even be able to set up a discount just for being a member or give them an added bonus of your own when they purchase through your affiliate url.

If decide to add affiliate links to your website, make certain the discounts you're offering is related to your main subject and valuable to its members.

Once you have decided which route to take, you need the right tools. There is abundant information around about how to start a membership site all the way to premier hosted applications. Sites like iLearn Online Marketing or My Membership Empire have vast training courses, membership site blueprints and materials.