This is cool. Would not know where to begin with gut renovation in Japan, though. And some of these look quite weathered. In US for example, you can typically sub-contract parts of the renovation to get decent pricing. One team for the basement flooring. One for waterproofing / sump pump installation. And then perhaps install drywall / paint DIY. Of course this is aided by close availability to Home Depot, Lowes, and…
Slightly off topic, but I was in rural Portugal recently, and my impression was that about one in three buildings was in some state of ruin, from otherwise delightful little cottages with holes in their roofs and empty windows, to remains of ancient walls just clinging together by the sheer will of their graffiti. (This isn't to pick on Portugal either - I've seen it in several different parts of Europe.) For the les…
Plus then you sometimes have issues due to ownership. It might belong to somebody in an old-people's-home who basically forgot about it. It might be part of an inheritance and the heirs are in conflict about what to do for many years. It might belong to somebody in another city, who doesn't want the trouble of selling and not the expense of fixing it and renting it out. The owner might also have an emotional attachment, and lacking the money to fix it. It might have been in the family for generations... etc etc.
It's surprising how many places are empty because the owners can't be bothered. It seems to me one of the better ways to find a way to live in German cities right now is to find an empty one, locate the owner and badger them into letting you rent it.
Then again, there is a political culture of squatting empty places as well, especially if they are derelict...
https://en.wikipedia.org/wiki/Squatting
(https://de.wikipedia.org/wiki/Hausbesetzung is a little better)