Simple payment site using Paypal (PHP, IPN)

A very simple (don't worry about front-end) site is needed that will allow users to register and to send a Paypal payment into a central account. The site should keep track of how much money has been deposited into the central account (the user's "balance") using Paypal's IPN API. Then at command of the user, money should be able to be taken from the central account and sent into the Paypal account of a second user. This transfer should be reflected in the first user's balance. Again, barely any front end design is needed. Basic HTML with PHP will suffice. MySQL database can be used to keep track of user info (name, password, balance).