Where to buy lost/disposed items?

I live in Osaka.

I wanna buy some furniture, A couple months back, my friend got contacted by another friend saying that someone died and all their furniture are to be disposed of. And if we want, we can go take a look and take what we like.

We went there with a keitruck and loaded up near pristine condition full leather sofa set along with some wardrobes and 1990s televisions in pristine condition. Same offer came to us when someone was demolishing a building next to one of our relatives and they asked us to go and take whatever we want before the demolition begun.

Now, I am in search for such opportunities. Where can one find/contact such people who dispose of the belongings of deceased people. Or items that people throw away or lost and never come back to take it? A treasure hunt.

I don't mind paying, but i have no idea how to search/find this informatiion.