What can we afford without having restless nights...

Many thanks for the helpful answers. I will first try to answer the questions for myself and then get back

To get a bit of a "feel" for the market, today we are looking at a plot of land for €200,000 (790 m2). If you take the frequently mentioned €2,000 per m2 for house construction in the forum (are incidental construction costs actually included in this rough guideline?), that would possibly be a realistic option for a house with 130 m2.

This is tight, just as an example:

Plot (connected?) including ancillary acquisition costs: 215,000

House 130m2 x 2000: 260,000

Additional construction costs: 40,000

Outdoor facilities: 20,000
Carport/Garage: 20,000
Kitchen/furniture/lamps/equipment etc.: 30,000

You see it’s heading towards 600k.
This is very rough now. It can all become significantly more (e.g. sloping plot).
I assume 130sqm without a basement, which would blow the calculation. If there isn’t one, consider that you still need square meters for technology, utility room, storage, etc. that might also cost.

I would look for a cheaper plot or an existing property.

Currently, financing is loose, still manageable with family planning but already more demanding. You have to ask yourself what you want. Many intend to go back to work immediately, not everyone does then. It’s not that easy after all. Maybe the second child comes soon, etc.
If you are aware of that, it’s okay. I’m quite glad we build only “after” family planning.

Thank you very much for the detailed list. I see it was good that I registered – with this calculation, the topic of building now seems to be far off – especially since these are already land prices if you move a bit further out into the countryside. That completely busts our budget. I was probably much too naive with my idea of getting a move-in ready house with a basement for €300,000.

Well, 220k for the plot and only 300k for the shell? Oh no...