Clubs and societies are a great place to like-minded people can join together. When you take such groups online and there are great opportunities for growth and also to provide more niche websites where people from all over the world can join together.
There are many membership plug-ins which allow you to create a site where people must join in order to get access to restricted content. In most cases you will leave some content available for everybody so prospective new members can get an idea of what’s the website is all about. However, you can then restrict content with the need for joining the site, which may include the payment of membership fee. Many plug-ins allow you to have multiple levels of membership if this is suitable for your use.
Maybe this use of membership sites is for the promotion and sale of information products. This started with Internet related information products that now includes subjects like dog walking, dog obedience, photography skills, cooking and much more.
Our WP business club dedicates Thursdays as teaching and membership presentations.