WooCommerce Product Trade-In Plugin allows you to mark your products as trade-in items in turn allowing users to sell you, the store owner their products. Create products just like any other WooCommerce product, give it variable conditions and pricing based on conditions such as color, size, product condition. User will then choose their conditions and be presented with an offer which you have indicated for that product. Once they choose to trade-in their item, they will choose a payment method in which they would like to get paid and will automatically be presented with a shipping label in order to ship in their item. You can then pay them once you receive the item.