New KfW Building Loan Conditions

The decisive factor for the KFW conditions is the loan agreement and the approval of the funding by the KfW after completion, but since you are building with a property developer, the financing must also be specified in the purchase contract. So you have no choice.

From my house bank I have the offer, since they only offer 18 months of interest-free availability period, they would now give me a written commitment before the purchase contract is signed that I have secured the following conditions for the next 6 months

I would then officially complete the financing within 6 months to achieve the interest-free availability period of around 24 months

Would I be able to access the new KFW conditions in this case?

When you conclude the purchase contract, the financing must be signed. This has nothing to do with the [bereitstellungsfreien Zeit]. The developer definitely wants a financing confirmation or something similar before signing the purchase contract, right?

No, the developer does not want to see any financing confirmation.
That wouldn’t be a problem anyway, it’s just a piece of paper confirming that the bank would grant me the loan.
Is it mandatory to complete the financing before signing the purchase contract?
If I complete the financing later, I also have no risk of interest rate increases since my house bank provides a written assurance to give me the currently listed conditions in 6 months.

Is it mandatory to complete the financing before the purchase contract?

Ask the developer what they require. From the builder's perspective, the financing should always be in place before the notary contract to avoid surprises. How great is the advantage of the new KfW conditions that you are willing to accept this uncertainty?

There is no uncertainty, as the bank assures me in writing that the conditions are secured and will definitely be granted after 6 months

new KFW €150,000 loan and approx. €26,000 repayment subsidy instead of €18,000

another advantage is that you do not have to take the loan from KFW; you can also, for example, take a cheaper loan from a bank and have the repayment subsidy paid out

these are definitely much better conditions