Is my house building plan realistic?

The danger for you is certainly not the current income. Rather, it is the desire to have children and possibly having only one salary for some time. You can currently only speculate when and how much your partner will earn again. As long as you cannot manage for several years on your salary alone, the risk is too high with such sums.

In addition, as already mentioned, we will eventually inherit 2 houses. And for old age, there are also capital life insurance policies worth about €200,000.

Don’t you think this plan will work? Or do I have a serious miscalculation? Of course, things can also go badly and in 10 years interest rates could be up at 6%, but such things can never be predicted.

First of all, cancel the expectation of the inheritance. No one can predict whether the houses won’t be sold to pay for care, senior living, illness, or similar.

A financing plan with current interest rates over only a 10-year term is short-sighted and could lead to financial problems in the future.

Including a salary increase in the financing plan from the outset is dangerous unless it is contractually guaranteed or you are a civil servant.

In my opinion, you are underestimating the costs for financing as well as ongoing costs for the house, children, and living expenses.

Certainly, building a house is doable. Whether you have to join the majority in the village is questionable! Would you also jump off a bridge if your buddy does? (Harsh example, but meant to encourage reflection.)
The daily struggle is well known to me through a colleague, and village communities impose pressures, but many families have financially ruined themselves trying to keep up!

Construction costs rise every year. Energy costs as well.
200 sqm need to be heated. Children become teenagers, secondary schools are not cheap... clothing, cosmetics, vacations, local festivals...

My grandmother used to say: Rome is in the smallest hut!

My tip: Go to the bank and get advice. After that, you will know your financial framework and can plan.

Good luck with the realization wishes Eve, who sold 240 sqm and built 155 new, because many sqm not only have to be heated and cleaned... there are also taxes, maintenance, and insurance.

Financing at the current interest rates over a term of only 10 years is short-sighted and could lead to financial problems in the future.

Including a salary increase in the financing plan from the outset is risky unless it is contractually guaranteed or you are a civil servant.

I don't necessarily think that a 10-year financing is worse than a longer one. Banks also plan interest rate increases in longer-term financings and don’t just offer a few years of cheap interest rates as a gift. In my calculation example, I saved so much in the first 10 years compared to a 15-year financing that I come out cheaper as long as the interest rates remain below 3.5% from year 11 onwards. At the same time, it might also be cheaper to refinance in 10 years than in 15 years, during which interest rates might be even higher. As I already wrote, I am now planning with 180 sqm; in my opinion, anything less is too small for 2 children. And yes, in my case I can plan a salary increase with 95% certainty. You can never fully secure all eventualities.

Then again, my question: How high does the net income have to be to afford a payment of €1160 when not living in a city with relatively high living costs?
(I know an acquaintance who moved to Munich from our area and told me after a year that the 50% higher salary he earns in the city all goes toward the higher living costs there)

For a €1,160 installment in an "expensive" city as a family with two children, I would plan a household income of about €3,500 – that is income from the man, woman, child benefits (for small children). Then, after housing costs of about €1,600 (estimated including additional costs, without reserves since it’s a new build), you have €1,900 left for living expenses = cars, daycare/childcare, food, vacation, insurance, etc.

For a €1,160 rent in an "expensive" city as a family with two children, I would plan for about €3,500 household income – so income from the man, woman, child benefits (for small children). Then after housing costs of about €1,600 (estimated including additional costs, without savings, since new building), you still have €1,900 left for living = cars, daycare/childcare, food, vacation, insurance, etc.

Ok, but now we have €4,500 income and live in the countryside or a small village with significantly lower living costs (daycare paid by the employer, etc.) That should work, even if one salary is somewhat smaller for a few years because of the children.

Hello,
that is very individual and cannot generally be said from my point of view.
You should honestly assess your spending situation for yourself (keep a household account book). Then also, if necessary, plan possible restrictions (parental leave, long-term illness, etc.) on your income. I would not include salary increases in your calculations, as the cost of living is constantly rising.
Regarding your planning with the 10-year financing: I can understand your arguments for wanting to agree on only a 10-year fixed interest rate. We did the same. However, you should then take interest rate hedging measures so that it does not cost you your house if the interest rate is 12% in 10 years.