551455 Invite system

Hello I am interested in an invite system to grow my e-mail lists. I will explain how it works 1. User will visit a landing page. 2. They need to register ( via facebook, simple registration form, linkedin, etc ) 3. They need to confirm their e-mail address 4. Each registered user should invite a number of users ( configurable via admin panel ) 5. Once this number of users will verify their e-mail address the main user will receive an e-mail with a download link. Please let me know how fast can you create such a script, and your price.