Database/user agreement and user info

Hi there,

I am looking to put together a site where people can register on the site and use the same login details to register on a forum and a business directory, but in order to register they have to pay a fee and also click on a user agreement.

I have read alot of forums and found these elements working independently, but not found anything which works together thus far.

Also, once people have registered, how do I have access to that user information?

Thankyou