It might be more expensive to fix than a new house due to location, lots of specialized manual labour needed (you cannot use eg standard window because the hole

It might be more expensive to fix than a new house due to location, lots of specialized manual labour needed (you cannot use eg standard window because the holes in the walls are non-standard etc) and regulation (concerning building codes, appearances (especially in such a prime old-town location) and, if you're unlucky, monument protection), and probably some issues with moisture that you'll have to address, etc etc., and everything but the walls need to be redone. 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://en.wikipedia.org/wiki/Squatting (https://de.wikipedia.org/wiki/Hausbesetzung https://de.wikipedia.org/wiki/Hausbesetzung is a little better)