Automatic domain name registration, and automatically creating an addon domain with document root folder

I am currently building an easy to use website building tool. please check it out here [login to view URL] There is currently a system that shows if the domain name is available or not and if it is available they can select it. I want when the person makes a payment that the domain name they selected will be bought and registered automatically and it will create an addon domain name and the Document Root folder for that domain.