> I wonder what we need to do to make buying and selling used items convenient
I'm not sure how feasible it is in practice. In theory I think you'd at least need the following to be possible:
(a) Being able to leave them literally outside your door in a manner that anyone in the neighborhood can see (basically impossible without additional technology for a lot of people)
(b) Being able to put them literally outside your door without causing issues (also impossible for many people due to everything from fire codes to simply lack of room or your own potential of tripping on them)
(c) Being able to make sure that anyone who takes them pays for them appropriately (nobody is going to keep an eye on them for free)
I'm not sure how feasible it is in practice. In theory I think you'd at least need the following to be possible:
(a) Being able to leave them literally outside your door in a manner that anyone in the neighborhood can see (basically impossible without additional technology for a lot of people)
(b) Being able to put them literally outside your door without causing issues (also impossible for many people due to everything from fire codes to simply lack of room or your own potential of tripping on them)
(c) Being able to make sure that anyone who takes them pays for them appropriately (nobody is going to keep an eye on them for free)