Which financing option should I choose?

The basis is the taxable annual income. This is not the same as the annual household income.

But the OP has already understood that. The OP will have around 70k, the wife as a teacher "only" 50k, so significantly less "taxable income" with a similar net income. Going from 120k to 90k will still not work.

I would do it as Johnny7 suggests: offer a 10-year fixed interest rate, you can bear the risk. A desirable feature would be the option to change the repayment rate so you can react if your wife does not become a lifetime civil servant after all. Assuming, for example, 1.7% nominal interest rate and a 1,700 euro installment, the calculated term is 19 years. In the first 10 years, you already save around 15,000 euros compared to a variant with 2.2% nominal interest rate.

The conditions after 10 years will not be that bad since you will then have 50% loan-to-value. You will most likely be able to afford even an interest rate increase to 7%.

The OP already understands that. The OP will have around 70k, the wife as a teacher "only" 50k, so significantly less "taxable income" with a similar net income. Going from 120k to 90k still won't be possible.

I would do it as Johnny7 suggests: offer a 10-year fixed interest rate, you can bear the risk after all. Ideally, this would include the option to change the repayment rate so you can react if your wife does not become a lifetime civil servant. Assuming 1.7% nominal interest and a 1,700 euro rate, the calculated term is 19 years. Over the first 10 years, you already save around 15,000 euros compared to a variant with 2.2% nominal interest.

The conditions after 10 years won't be that bad since you will then have a 50% loan-to-value ratio. You will most likely even be able to afford a rate increase to 7% then.

Yes, you are right, it will be difficult to reach 90k€ with a child.

It is what it is. My zvE is more than 30k below the gross income. Advertising expenses down, insurance contributions down, child allowances down. That goes quickly.

Of course, you save the Baukindergeld for ten years in a useless mini home savings plan to cover the remaining debt of the equally useless KFW 124 (50k€) building block with a 10-year term.

However, I find zabas' idea as substitute equity understandable. The benefit is guaranteed by the state. With a corresponding lock on the payout account, wouldn't that be usable as collateral in the financing?!

by now you are completely off-topic. He asks, Boskop apple or Granny Smith apple? You say, take bananas. I see, option 1 leaves an outstanding balance, option 2 does not. But both have similar monthly burdens, option 2 doesn’t cost much more per month than 1. So option 2. And the building society savings contract, why BHW? In my eyes that is quite an unreliable building society, under the aegis of Postbank they have moved far away from Beamtenheimstättenwerk. Has Dr. Klein only BHW? Or are they just particularly cheap in your case? Our building society was always Aachener, and I have found them very fair in their advice. Karsten

Why exactly the BHW, I really can't say, that was just suggested by Dr. Klein. What I also didn't know about the building society savings option is that the building society can refuse me the loan in the worst case. And when I already read here that the BHW is unscrupulous, I'd rather keep my hands off it. I will approach Dr. Klein again.

No, she cannot refuse. Once the contract is funded and allocated, you have a right to the loan. That's the deal. The loan is always interest-bearing as agreed at the time of conclusion, the credit is always without land register and always comes with the right to special repayments in any amount. That's how I know it. Karsten