Is it possible to buy/finance a house during the separation year?

Accrued gains are not only calculated at the date of the divorce. The date of separation is also important.

At the time of separation, she had nothing from which he could receive any accrued gains. It’s all about the future. She understood it so that the day of the divorce is basically the cutoff date for who owns which assets.

Currently, the situation is such that she has claims for accrued gains from him.

I will pass on the tip about the big bank. The intermediary did not mention it..

That is a bit illogical – he cannot make claims on the house because he is not listed in the land register. The only thing that counts is the accrued gain, meaning the increase in assets. For this, it does not matter whether the assets exist as cash or as equity in the house. It is the same amount either way.
The only thing to keep in mind is that enough cash is retained to pay out the partner in case her accrued gain is higher than his. Because if she put all the money into the house, then obviously she would have a problem in that case.

With the claim, the bank meant the accrued gain. But can an accrued gain arise if she finances the house 100% (possibly even more than 100%, including ancillary costs), does not begin repayment, and does not renovate for the time being? She would only start paying the interest rate.

In that case, there would be nothing but debt. Or would the possible accrued gain still be assessed based on the market value of the house from the time of purchase until the divorce?

By the claim, the bank meant the increase in value. But can an increase arise if they finance the house 100% (possibly even more than 100%, including incidental costs), do not start any repayment, and initially do not renovate anything? They would only begin to pay the interest rate.

The bank has no idea who is entitled to what. Neither in the case of equalization of accrued gains nor in maintenance. Only what is written or agreed upon in black and white counts. How is the bank supposed to know that, independent of the house, there might still be several hundred thousand euros to be compensated to the man?
It’s like with income. You cannot say, "I earn 20,000 net," without being able to present pay slips or tax assessments. Loans are rarely granted based on your word alone.

The bank has no idea who is entitled to what. Neither in the case of the division of increase in value nor in maintenance. Only what is written or agreed upon in black and white counts. How is the bank supposed to know that aside from the house, maybe several hundred thousand euros still have to be compensated to the man? It’s like with income. You can’t say “I earn 20,000 net” without being able to present pay slips or tax assessments. Loans are rarely given based on your word alone.

Correct! A bank wants solvent borrowers and no uncertainties on the books

By the claim, the bank meant the appreciation. But can appreciation occur if she finances the house 100% (possibly even more than 100%, including incidental costs), does not start repayment, and initially does not renovate anything. She would merely start paying the interest rate.

It does not really matter whether she will make a gain with the house, but it is enough that the house increases in value by itself, for example due to rising land reference values, new highway connections, or similar. The house can indeed be worth more after 1-2 years than she pays today. This is a general chance or risk, like a new landfill site in the neighborhood (exaggerated).

However, the actual problem of the banks has been well described by my two predecessors.

I have another idea:

How about a lease purchase for x years until the divorce is finalized?
Would the seller be willing to do that?

Would your husband be willing to agree to separate property from now on? It might also be advantageous for him.