Construction in the Munich district, realistic?

Yes, you have to optimize a bit, but the project is feasible. I mean, here some are building with 1200 per m2...

But in Saarland and not in the district of Munich. And you should mention that the client is a trained installer and does almost the entire technical equipment himself plus laying tiles and and and...

I don't think this is an option for the OP now.

Because of the civil service? But that also doesn't sound like much desired EL.

Smart home, of course, has a stronger impact on the price per square meter in smaller houses. In our case, I assume about 200 EUR per m², so there would still be 3800 to 4300 left, which is still expensive.

The feasibility always depends on how securely a required loan can be repaid. I would include the expected value of the property in the decision-making process. €1200 / sqm is no problem, as long as it does not decrease; only liquidity must be adequate. With a house built too cheaply, the value of the property will be reduced.

Our self-saved equity went into furnishing our current apartment 4 years ago (kitchen, electric shutters, awning were a big part) and last year we bought a caravan.

So you have consumed quite a bit. Would you want to restrict yourselves in the future? And how did you calculate the price for the semi-detached house? It seems rather low to me compared to the plot of land.

So we are building directly in Munich and will probably end up at around 5000/sqm all in if I have the numbers right in my head...

You are not building a single-family house/TH either, where the costs are probably even higher. But it remains the case that Munich lives up to its reputation.