backend programing work on website

Hello, Here is what we will need, rather simple. We will need a system to manage user accounts on our site. So like the user creates an account on our website and then they log-in using the username and password that they specified. And when they create the account an automated email is sent to their address. We will also need some kind of system to bill the customer's credit card monthly, or just once for a whole year's worth. Then of course we need a database to to keep track of the usernames, passwords, credit card numbers, etc. The users will purchase membership to the site to receive cuponds, so we will need something that can generate these with the users name on it. We will also be selling merchandise in the future so we will need a system to handle that. We have the website designed, all we need is to add this functionality to the site. We will need this completed and tested by the first of May.