Use own capital or borrowed capital for a single-family house?

But that works. Just call around a bit, then you'll find a bank. In extreme cases, they don't even want a land register entry as security...

Then I would be stupid not to take out a loan from KfW if I get money "given"?!

Even really stupid. Of course, always offset with the additional costs for energy consultants, interest, and extra insulation measures.

After consulting with the tax advisor, as much debt as possible should be taken on the rented apartments. If possible, this part should also not be repaid.

After consulting with the tax advisor, as much debt as possible should be taken out on the rented apartments. If possible, do not repay this part either.

And are you now the spouse of or have you, out of charity for the benefit of a forum member, inquired with your tax advisor on how to do it?
Because surely does not have a second identity in this forum, right?

...apart from that, hopefully you have not paid a huge fee to the tax advisor for this piece of insane insight?

after consultation with the tax advisor, as much debt as possible should be taken on the rented apartments. If possible, this part should not be repaid either.

Thank you for this free information The apartments are 100% financed and the loan will continue.