Buyback

I am looking for a simple barebone script (no bugs or flaws acceptable) designed in PHP. The script will be designed for users to navigate the site to find products we are buying back. The user should be able to view the products and the prices we are paying. Users select quantity of items to sellback and fills out payment information and submits it to the server. The admin side should be able to Add/Edit Products & Prices into categories. View orders waiting to be received as PAID or RETURNED. This project is intended to be simple but allow for expandability down the road. If the system proves successful for the company, more features will be developed.