OK, isn't €250k "without land" a large budget for a "normal single-family house"? Including land, that's €350k! We don't need golden faucets! We previously had a bungalow that we partially built ourselves with own labor. Yes, okay, that was 15 years ago but it cost less than the planned single-family house. I'm somewhat speechless! People, that's a quarter of a million euros!
*wiping tears of laughter from my eyes* Sorry, but I just can't help it right now. How can anyone be so naive to buy a plot of land without having the slightest idea what a normal single-family house costs? €250k is really tight. You can't even think about golden faucets. More like the cheapest tiles, simple plastic windows, and the cheapest doors the general contractor offers.
You can go lower if you contribute A LOT of your own labor. Here in Munich's commuter belt, a price of €2,000 or more per square meter is calculated for a simple single-family house. But then you get laminate flooring, not parquet.
That's definitely not a large budget. What about your own labor? Are you handy? Do you have someone in the family/friend circle who can help? Keep in mind that own labor usually significantly extends the construction time, but the general contractor already wants to be paid. That means you pay rent and also start repaying the house loan at the same time.
If you're that tight on budget, then calculate very precisely what you can afford and what you can't and compare the construction descriptions meticulously, so you don't get a nasty surprise.
I would still recommend a buffer of €10,000-20,000. Usually, something unforeseen comes up and the overall project shouldn't fail because of that.