Feasibility financing new construction (land + semi-detached house or semi-detached half)

Housing costs: per month 768,- EUR (employer apartment, our big advantage)

[*]current cold rent: 440,- EUR
[*]current warm rent: 588,- EUR

How big is the apartment?
If it's too small, is there perhaps a larger alternative through the employer?
Because I think you can hardly live cheaper in the Stuttgart area.

There are some banks that would finance my project, that wouldn’t even be the biggest problem here. It’s more about the fact that the banks don’t want to grant me the loan at the current conditions, but only at the time of development and start of construction, which would probably be at the end of this year. Until then, the interest rates will certainly continue to rise, and of course we would prefer to repay principal rather than just paying interest.

I doubt that there are some banks and then not at good interest rates. Normally, a loan agreement with fixed interest rates and a commitment period of 6-12 months is signed when the plot is purchased.

the "only" thing you could still try here is to shift the repayment "backwards," i.e. if you say: the wife is going to start working soon, that will bring in €1,000 per month = that relaxes everything.

The wife is a cashier, even if the minimum wage is increased soon, €1,000 net is almost 40 hours/week and that with 3 small children

The woman is a cashier, even if the minimum wage will soon be increased, 1000.-- net for almost 40 hours / week and that with 3 small children

so postponing it is in 15/20 years!

then the children are no longer small (probably already of legal age) and if you plan well, and still have an interest rate of 2.0-2.5%, and of course high repayment, then it should work.

and I assume that in 20 years a "cashier" will earn more than 1000€ net.

with the current inflation of 6%, I don’t want to know what the costs for rent/property will be like in 10-20 years...
hopefully incomes will be adjusted accordingly...

The woman is a cashier, even if the minimum wage will be increased soon, 1000.-- net for almost 40 hours/week and that with 3 small children

Minimum wage and a 40-hour week with tax class 4 and 1.5 child allowances results in 1487 net. To achieve 1000 net with minimum wage, considering the sliding scale zone currently requires about 1270 gross, which is about 25 hours/week. And, depending on where one is a cashier, the hourly wage is higher than 12 euros.

Since the man earns more, but not enough for the loan, tax class 3/5 would be better than 4/4. Whether it is 30/35 or 40 hours is not decisive, but it is a completely different ballpark than 20 hours. Postponing the larger repayment until the children are grown leads to American conditions. There, it is not planned to pay off the house at all; instead, a smaller/cheaper one is simply bought in old age, and the repayment is the difference between the two houses (minus the new car).