As this project appears to be fairly unknown in the fediverse still, I’d like to use this opportunity to advertise Flohmarkt. This Fediverse equivalent of Facebook Marketplace already has some instances up and running - see here: https://codeberg.org/flohmarkt/flohmarkt/wiki/flohmarkt-instances
Maybe share your vision with the devs or actively contribute yourself to the development of this platform? :)