Cost planning - core renovation of farmhouse / country house

Maybe we are talking about different properties, but I also find old holdings here with large plots and no directly adjacent neighbors that do not look like former agricultural land. So where there is now no stable or hall or anything like that. Maybe I'm mistaken, no idea.

But the argument

What was once built on can never be used as arable land again.

doesn't that suggest that it is better to renovate and continue to use the existing building rather than let it decay or demolish it? If it’s already there and uses up former pasture land, why would anyone want to put obstacles in the way of people who want to repurpose it?

That referred to the comment before me, which described that farm owners are no longer allowed to cash in unused grassland.

But the argument

doesn't it rather suggest that one should better renovate and continue to use the existing building than let it decay or demolish it? If it already stands and uses up former pasture land, why would anyone want to put obstacles in the way of people who want to reuse it?

that the existing building is then better renovated and reused, rather than letting it decay or demolishing it?

No. In the outer area, building is not allowed and should not be done. This has more to do with preventing municipalities from becoming sprawling. So only agriculture (or whatever else in the outer area), existing rights protection (if agriculture is no longer practiced), or demolition. This is also good and is enforced quite consistently. There are plenty of properties in the more rural outer areas of cities and municipalities that you are looking for – lots of land and you don't notice the neighbors. I live in such a property myself and am in the midst of the nearest metropolitan areas within 20-30 minutes (35 minutes to Düsseldorf’s Königsallee or 20 minutes to Duisburg city center).

There are plenty of properties in the more rural outskirts of cities and towns that you are looking for – lots of land and you don't hear anything from the neighbors. I myself live in such a property and can be right in the middle of the nearest metropolitan areas within 20-30 minutes (35 minutes to Düsseldorf's Königsallee or 20 minutes to Duisburg city center).

But I'm not allowed to do anything to the properties then, am I?

Starting points on how a restoration could proceed can be found, for example, at

Architekturbüro und Zimmerei Enno Reinstorf (Google)

Outdoor areas are very difficult to get approved even with us. Neither stables nor machinery are welcome in towns - they must be placed outside, the rest must be inside the town.