Buy a 25-year-old shell structure

The entire meadow below would also belong to the property, approximately 5000m2 of agricultural land

Decades-old shell construction that is closed but unheated and had no protection against weather?

No offense, that screams wrecking ball. No need to get your hopes up.

For me as a layperson, the masonry basically looks intact, but of course that can be misleading. I would be interested in the opinion of a mason here if one is present. I will also not take any risks here as I do not have money to throw away. However, I have heard from other groups about some cases where there were no problems with a "slightly" delayed completion.

I have heard from other groups about some cases where there were no problems with a "slightly" delayed completion.

That may be so. Nevertheless, you will have to redo the majority of the house including the building application completely. And regarding the location: That is ideal for you. Otherwise, it is really at the AdW – says Aunt Google. No wonder hardly anyone wants to go there.

Jettenbach near Beilstein, Heilbronn area? If yes, calling it a top location near Stuttgart is massively exaggerated. I don’t know the area just from Google Maps either, and it’s absolutely dead there. The highway or nearest federal road is quite a distance away. We built a few kilometers further away. The standard land value here is €385. However, we are 500m from the federal road and 3km from the highway. I don’t think the land value where you are is €200. Therefore, it’s too expensive and risky.

If that thing is your dream, go for it. Factor in a big uncertainty margin in your calculations and be happy if you manage with less. Such projects are actually for people who take the financing because of the interest advantage and have the money saved up. Economically speaking, the situation is rather affordable and by no means sold out. Alternatives should be fairly easy to find.