Build an electronics trade-in site

We are look to have a website build that functions like Gazelle.com. We are only interested in the SELL portion of this site. Users can get a free quote on their used electronics after answering some questions about their item. Once they answer the questions a price will be shown for that item. Next they will enter how they would like to be paid. Next they will print of a generated shipping label and send the item into us. On the backend, we will need to send the user an update when we receive their item and that it is being evaluated. Once complete, we will issue them a payment via their previous selected choice and we will send verification of payment sent to them. On the backend we will also need the ability to add new items as they come. An agrithium needs to be developed that will automatically know what price to access to an item for the correct value based of answers the user elects.