Buying property with a house blindly? Risks?

Risk 1: You are not allowed to build what you really want there. Check with the building authority and building regulations, as well as possibly protected trees. Also possibly clarify monument protection.
Risk 2: The demolition will be more expensive because, for example, an oil tank needs to be disposed of. Go and take a look and plan a generous demolition budget.
Risk 3: No neighbor wants anything there, the atmosphere is contentious and hostile. Just ring the doorbell next door and ask politely. The first impression is enough.

Everything goes very quickly.

Thank you very much for the information so far.

A possible problem is the following: We would have 3m distance on both sides from our house to the property boundary. The neighbor on one side only has 2m distance. Currently, 3m is required.
Do you have experience with the building authority? Is something like this still approved? Is it perhaps possible to work with special fire protection walls?

A possible problem is the following: We would have a 3m distance on both sides from our house to the property boundary. The neighbor on one side himself only has 2m distance. Currently, 3m are required.

This has generally been the case for a longer time and smells like a setback area takeover (what does the land register sheet say about this?). That would mean at least four meters on your side there.

This has usually been the case for a long time and smells like the assumption of setback areas (what does the land register sheet say about that?). That would mean at least four meters on your side there.

A building encumbrance is not registered on our property.

Especially the idea of spontaneously approaching the neighbors I find good. They might know about "Grundstücksprobleme" and at the same time, you immediately notice the mood and who you might have to deal with later ...

"... on our property ..." ... you have probably already mentally acquired it ... ;)

We are still optimistic ;) The house is to be built in the same location as the old house, just longer. Is there any existing rights protection? Probably not in case of demolition, right?