Despite the fact that the Internet is populated forums, there is also an opportunity to create private, where members must pay a single or recurring fee to join.
SEO Blackhat charges $ 100 monthly from its members, and they have thousands of them. Obviously, in order to charge a price for a forum membership you need to provide real value to members (eg, secret techniques, tools, etc.).
Performancing also recently started a private forum, focused on the network aspect. She called the hive and the monthly cost is $ 10.
These are just two examples. There are many opportunities to create private and profitable forum, you just need to find an attractive angle that make it valuable for the participants.
List of popular forum software:
* vBulletin
* Simple Machines Forum
* phpBB
* Vanilla