House construction in Baden-Württemberg - Planner first or bank?

As said: Like this or something similar. For now, better not hold on to 10k. But you will quickly notice how much house you can get for that amount (or not).

And keep in mind that you can somehow tweak and adjust any number.

But a piece of advice: I would only go below 5% p.a. for the annuity with very, very good reasons. Today, expecting 1 to 2% repayment is, in my opinion, not responsible, unless larger cash payments can be planned for the future (though there are always some anyway).

What is your family income and what do you imagine as an affordable installment? Do you think you can afford it?

That's also a thing... Currently, the joint net income is around €4,100. After analyzing the household budget, I identified a current amount of about €1,800 for the expenses of a house. That corresponds to about 43%. However, my wife is currently working part-time. This is supposed/will change again in the next few years when she works more or takes another year of parental leave and receives parental allowance. (How) do you factor in such income changes?

That's also a thing...
Currently, the combined net income is around €4,100.
From analyzing the household budget book, I have determined a current amount of about €1,800 for the expenses of a house. That corresponds to about 43%.
However, my wife is currently working part-time. That is going to change in the next few years when she works more again or takes another year of parental leave and receives parental allowance.

(How) do you factor in such income changes?

To be honest, not at all! The bank doesn’t do that either. They assume the actual income. If there is more income at some point, good for you. Then you can make special repayments. Increasing working hours (if that ever happens) takes place in a phase of life when the loan is already in its last third. With €4,100 and further desire to have children, you should consider how to protect yourself against death/disability of the main earner. With this income, I advise you to take out a maximum of €250k.

Thank you for your feedback. To be honest, somewhat sobering, but of course I am grateful for honest and realistic assessments from your side.

I am curious about what our first conversation with our house bank will yield.

You can report, I think the bank easily says 400,000€. They don't give you life advice...