What remains to you as a reserve?

What question (with what background) is this collection thread supposed to clarify?

I am now imagining it like this: a) 1000 euros, b) 200 euros, c) 50 euros, d) 500 euros

This is really a sincere question! I would like to have a reasoned answer to it.

Otherwise, please delete, close, or do something else. I only see, on the one hand, the possibility that those with a good income pat themselves on the back and, on the other hand, a discouragement for those who are generally in a tight financial situation but for whom financing can still work in individual cases.

New building: No reserve fund in the first years, as in my opinion it is not necessary. We ourselves have not saved an extra euro as a reserve fund for the house in the last (almost 20) years. That does not mean that we do not save nevertheless.

Not much happens in the first 5-10 years either, so a reserve fund is not required. Applying new wallpaper or paint to the wall should be possible from the ongoing income.
If you cannot build up even a (small) reserve and still perhaps need a new heating system (that can happen), you can always go to the bank and apply for an increase in the mortgage. Hopefully, it has been paid off by then at more than 1% ;)

And then?
Eventually, other things will come too. New exterior plaster, bathroom renovation, roof renovation, etc........ Do you always want to run to the bank then?

No, well, that definitely wouldn't be for me. I don't want to spend my whole life dependent on a bank and in debt. It’s clear that for almost everyone, buying or building a house is linked to a loan. But I hope this will be the only loan we ever have and that it will hopefully be paid off after a maximum of 20-25 years. For the rest, I prefer to be responsible myself and not tied to a lender, even if that means in doubt I have money "lying around" somewhere "pointlessly" (because it’s not invested/consumed or hardly/no interest). In the end, everyone has to make this decision personally and be happy and satisfied with it.

Neither the meaning of the question nor the answers and conclusions are clear to me here ...

1000 before child, 500 after child

And then?
Eventually other things come up too. New exterior plaster, bathroom renovation, roof renovation, etc........ Do you want to keep running to the bank then?

No, definitely not for me. I don't want to put myself in dependence on a bank and have debts my whole life. It is clear that for almost everyone, buying or building a house is associated with a loan. But I hope that this will be the only loan we ever have and that it will hopefully be paid off after a maximum of 20-25 years. For the rest, I prefer to be responsible myself and not tied to a lender, even if that means in the worst case that I have money lying around somewhere "pointlessly" (because it is not invested/consumed or has little/no interest). In the end, everyone has to make this decision personally and be happy and satisfied with it.

When will the new exterior plaster come? For our new house probably only when I'm dead :( - so after about 40 years. The bathrooms are just a few months old right now, I definitely won't spend 20,000 EUR on a new bathroom in 5 years, the roof also lasts 40-60 years. So why should I form a reserve now?
If after 10 years (besides the savings rates I have anyway) I specifically save for heating (in another 10 years) or bathroom (maybe in another 5-10 years), then that's OK!

Everyone can do as they like, but I don't want to make myself a hostage to my house. That's how you summed it up in your conclusion anyway.

From gut feeling, and my experience with the homeowners' association administration, I would put aside 1,000 to 1,500 EUR per year for an average house - starting from about the 10th "year of life" of the house. So much for the OP's question.