Custom PHP Script Modification

I am looking for someone to modify a php scrip that I have on my site [login to view URL] Right now users can upload their beats and share them but I need a option for the users to be able to sell their beats as well. If you go here [login to view URL] I want there to be a "buy now" buttons next to the "Share" buttons. When the visitor clicks this a light box will pop up asking the user to select a license type. Once the visitor selects a license type it will add the license to their cart. The light box will have to display the license names/descriptions/prices/and file that comes with that license, example: .mp3,.wav or .zip Since the products are all digital goods the checkout will be simple. It will ask for full name, email address and the option to checkout with "Credit Card (Stripe Payments)" or "Paypal". Once the user completes the payment the file will be sent to the provided email address. I would also like for the user to be able to have a download link in their account page. All of the payments would go to either my paypal account or bank account attached to (Stripe Payments) I would also need to automatically be able to pay the sellers weekly via paypal or bank transfer (Stripe Payments). Note, I will also be taking 25% from each sale before the sellers get paid out. I also have a few more modifications that I would like to make if this goes well Thanks!