G2 Adapting site to work for Paying members only

I was playing with Edit Album tonight and activated the username and password to access that album. How would you go about making it access an entire new SQL table (same g2 database) that has a login/password/ID table that I can use an entire different system that when you access the site and choose to join, you pay with the credit card, once its approved it gives you a login and password (login is unique) and with that login and password to you could access that album.

I supposed an easier solution is make your g2 directory have an .htaccess and the only way to see anything in the gallery would use the MySQL authentication system with the .htaccess, and install a second gallery for the free area.

Any Ideas? I really need to get something together for a few people that has this ability and I don't know much PHP