Web Developer for building an advanced form

I would like to build a site similar to that of yousendit.com. The difference would be that income would be generated through advertising. People can head to the web page, upload a large file that emails dont usually permit. And send it to an email address of their choice with a message. The recipient receives the email with a link that will let them download the file from the server.
The sender would also need to receive a confirmation email.
I would also need as much access as possible to the site and its code.