Financing - what is realistic?

Your original plan looks by far better. New construction, as you already said, is mathematically okay. Whether it actually works out in reality, I would simulate for at least one year. I would advise setting aside at least €1500 monthly "for the house". Additionally (in a different account), money must be saved for the household items that might break (the car is then at the very top of the list).

In your situation, you can afford a little house. But there are two things standing in your way, and at least one of them would have to be changed to make it realistic for you.

1. You are the sole breadwinner. Can't your wife at least work part-time?
2. You have very high living costs. I don't want to discuss here why they are so high; you have to figure that out yourselves.

But as a comparison: same profession on my side, not quite as high a salary (since I've probably been in the profession fewer years than you), but my husband also has a full salary (which is lower). We have one less child, but we don't live very frugally and still have two full daycare fees, which you probably don't have. And still, we don't even come close to spending a good 3000 € a month on living expenses. So you should analyze why that is.

There are only two possibilities: either you increase your income or you reduce your expenses.

Hello, I have been maintaining an Excel sheet for quite some time, so the numbers might be a bit more accurate. According to that, the current situation looks like this:
- Income: €4,288.00 (sole earner plus child benefit)
- Ongoing costs total: €1,652.50 or 38.5% of the income (of which €550 is cold rent)
- Income minus ongoing costs: €2,635.50

Less the monthly saved €200, we have therefore spent about €2,435 monthly on clothing, food, and consumption, which means about €487 per person for 2 adults and 3 children. This can certainly be reduced to some extent.

PS: My wife wants to work again sometime, but as a nurse, she doesn’t earn much anyway and if you offset the additional costs (commuting -> a second car necessary, childcare) for, e.g., a €450 job and the organizational effort*, then we don’t gain anything from it.

*(Problems when a child gets sick and has to stay home, the employer demands shift work/night shifts/overtime, etc., and unfortunately we don’t have any grandparents nearby who can look after 3 (!) small children at short notice. That unfortunately doesn’t work at the moment. Maybe in a few years)

Wohnriester is unfortunately out, since we already "riestern" conventionally.

You can use the registered money including the allowances for a house and then do [wohnriestern]. Just as a note.

“laufende Kosten” are only fixed costs, right?
A detailed analysis of all costs over a year would be necessary.

You are a businessman after all. It should be possible for you to analyze the variable expenses in the private sector a bit more precisely.

Phew, almost two and a half thousand euros just for consumption? I find that extremely high, even with three children. It's not like you have a particularly high rent either. So try to find out why you are spending so much and whether it is realistic to reduce the expenses. If not, then you will probably have to at least postpone or give up your dream of a house.

2435 euros for the LHK of 5 people are already significantly above average. Even some generously and cautiously chosen flat rates of some banks are below that. So potential is basically still available, as you yourself recognize. However, such a thing is not easy.

I would like to have the income of a nurse with an additional function (PDL). As a 450 euro job or at 20 hours/week it is not necessarily something.

On the other hand, I know a couple in my circle of acquaintances, both nurses, where he works full time and she works 20 hours/week and they have one child and have financed a 350,000 euro house at 80%. So it is possible.