Add user login to purchase.php

I would like to add a user login to my [login to view URL] page that will store the user name & password of real estate agents and allow them to login when they come back again. When they loging it will remember all their contact info. Page is at [login to view URL] I only have one MySQL database with my host...can I still do this? Using 2 fields of the database already. ## Deliverables 1) Complete and fully-functional working program(s) in executable form as well as complete source code of all work done. 2) Installation package that will install the software (in ready-to-run condition) on the platform(s) specified in this bid request. 3) Complete ownership and distribution copyrights to all work purchased. ## Platform IE