I'm not sure if there's something similar already.
I've been selling a lot recently. Some stuff that I don't use anymore. Clothes, shoes, bikes and other stuff.
The idea is to build a web app that allows you to make a listing and share it with the buyers for them to make an ONO (Or near offer).
I can see that this can be useful if you're selling your car or house and you want to get the best price as possible.