Old building renovation, house built in 1916, multi-family house converted to single-family home, experiences

Hello everyone, We have the opportunity to take over a very old house built in 1916. Currently, it is divided into two rental units, and we would then turn it into a single-family home. So far, we only have rough key data such as the year built, about 170 sqm of living space in total, heating is 20 years old, and the windows are new. That’s not much, but that’s not important at first. That will come later if necessary ;) For now, I want to ask if anyone has ever renovated such an old building? What are the classic things you have to prepare for? You can find quite a bit on the internet, but I would like to hear direct experiences as well. I assume that over the years only maintenance has been done and no renovation. Thank you very much! As I said, there is not much information yet, we are still at the very beginning of the journey.

1916 is not old yet :D. Ours is from 1921. those are construction years shortly after the First World War. Our house, for example, is built very solidly, but simply, which is typical. We have had no problems. What kind of house is it?

It is an old villa with many wooden elements, etc. Still with a beautiful large garden and conservatory and spacious entrance area. Did you have any problems in the basement or intermediate ceilings?

I'm just working on it. Much will only come up later.…

but we completely rely on the masonry and then build on it again. You can certainly see a bit more than if you just peel off wallpaper and paint ;-)

Electricity is always exciting, hidden doors behind wallpaper too. I would take a closer look at water pipes, heating system, and basement. What kind of roof? finished? Building permits for all above-ground structures available? Drainage of the property? Possible border conflicts with neighbors? (overbuildings, fence, wall, garage, carport etc…)

My main concern is, has anyone here ever renovated such an old building?

I'm more or less done with my renovation – although it’s from the 60s. But at that point, it hardly matters how old the house actually is.
I would say: Everything new is on the agenda.
There aren’t really any special features. You probably have a refined shell if it’s been gutted once. And then it’s basically a 1:1 equivalent of a new build. Except that the floor plan and window sizes/number or similar might be outdated and possibly need to be adjusted.

Yes, that is our plan. Everything out except for the bare wall and then off we go. I would like to install a photovoltaic system in combination with a heat pump, but I have read that it is not so easy in an old building. I am basically assuming unseen costs of 250-300k€ for the renovation.