Anyone else, feel free to correct me if I'm wrong, but:
You build the site. You're responsible for the content, advertising, tour pages, members area, etc... it's all at your control. The AVS program handles the credit card processing.
If someone buys access to the AVS program, they get a password. With that password the surfer now has access to all sites that use the AVS system, including yours.
You get paid whenever someone signs up with the AVS system.
From what I've been told, AVS rebills can be nice.
