Is a single-family house possible for 180k €?

No. The entire construction costs.

By doing the work yourself, simply put, you can only save on labor costs and the VAT on them. So, you save the most when using many hours (logically, in other words: labor-intensive trades) and preferably for high-wage activities (you would have to be an architect or a KNX programmer).

Additional savings might be hidden in the profit margin of the materials, but you do not have the purchasing power that companies possibly have (discounts).

Then you still need tools…

My conclusion: This only really pays off if you have someone to guide you (father & uncle have already built 3 houses) or are a professional yourself.

That's the point. Masonry work, for example, is labor-intensive. There is certainly more than a halving of the costs possible there. Roofing as well. Carpentry, well, that requires quite a bit of machinery, a crane, etc., to lift a roof truss like that. Not really something for do-it-yourself. But tiles/plumbing, countless people do that themselves with the golden Hornbach card. Heating system, that also takes many hours, and if you know how to do it, you can halve the costs there too. Conclusion: If we take our 166 from above as a benchmark, you can definitely reduce it by 50. If you can do it. I can't, so I have to pay. That's just how it is.

is the house already there?

is the house already built?

I would be interested too. The prices are outrageous. Complete electrical installation labor + materials in a single-family house for €4600? Nope...

Base slab, garage, now they are building with Ytong.