New construction - What is included in our financial budget?

Hello, we might possibly build a house. We have a net income of about €4000-4200 left over. I will turn 39 in October and will probably retire at 62. Of course, I would like to be debt-free by retirement. We have 2 children and no high standard of living. Naturally, one would also like to go on vacation sometimes. What kind of repayment could we approximately afford? Regards Christoph

I'll ask the other way around. What do you want to afford? What is the current equity, and what is the monthly savings rate? How much do you pay for rent including utilities?

What does 4000 leftover mean?
4000 savings after all expenses at the end of the month?

Currently paying hardly any rent because we live in my parents' house. Unfortunately, it is too small. Now we can get a plot of land with 520sqm for €22,300. Unfortunately, there is not much equity, but we could do quite a bit ourselves. We thought of a house with 130 - 150sqm with a gable roof. Is €1000 repayment too much? Additional costs will still come...

If we add up all the costs we currently have, such as insurance, vehicles, groceries... about €2800 remain.

The question always arises first, if 2800 is left over, why didn't you save 30000€ in equity last year. You can honestly answer for yourselves what is actually left over. But basically, a normal single-family house on such an inexpensive plot should be feasible with the income. To be finished by retirement, this would mean a monthly burden of repayment and interest of about 1500€ plus additional costs, so you have to expect a higher burden of about 2000€.