I love this idea because I think this is a huge win-win for both buyers, sellers, and efficiency (more stuff gets used, less gets tossed).

As the comments have pointed out the difficulty is accurately identifying items.

With used books you don't have that problem because every book has an ISBN number so you can easily identify any book. That's enabled a robust used book market.

So maybe the business isn't the end product, maybe the business is an intermediate step, the equivalent to ISBN numbers for everything.

The business I'm thinking of is QR tags for everything. The QR code allows the owner to simply scan the QR code when they want to sell their stuff.

You'd have to work with OEMs. The pitch to the OEMs is that a QR code that allows the item to be identified and easily resold enhances the resale value, thus enhancing the initial value of the item.