Buying a house without a mortgage loan

She unfortunately reacted a bit cranky when I said that I wanted to have an expert take a look because I have no idea if I am overextending myself financially since I have to commit to renovation measures.

I think you first have to be very patient and collect the documents together with her. Simply always offer to take over everything; if in doubt, she should sign powers of attorney so that you, for example, can obtain the land register extract from the authorities. It will all take time, but you can't really put much pressure on her. If the expert is a problem, maybe you can finesse it so that the bank wants someone "official" to record and draw a simple floor plan because without a floor plan, there is no loan. Perhaps an argument like this will help.

Since the house is too much for her herself, I do believe that she will accept the appraiser with the argument "that I don't overextend myself." She has the land register excerpt, as well as the [Flurkarte]. She has offered to take the living area measurements. The floor plans would then have to be created somehow.

She will at least carry out the living space calculation. I can't do that because the house is full of stuff

Of course you can. Grab a laser measuring device for 20€ and measure the rooms. Do you really think you can rely on the seller???

Laser measuring device I completely ignored it. Alright, I'll get it.

But can I also simply take out any random loan for any random amount, for free use?

Consumer credit is expensive, but doable. You can also borrow the money from a private person (private individual).
Just suggested like that… whether that's really the right thing, I doubt it.

I would need about €110,000. Purely for the purchase.

If that’s enough. Notary, etc. also has to be paid. And then there is the renovation. You can easily reach four figures at a hardware store purchase. And always waiting for the next month is also annoying.

If a living space calculation is a floor plan with calculated areas, then you can manage that yourself. Exactly!

The 110,000 is supplemented by 20k equity, which is sufficient for the pure house purchase including notary and property transfer tax. And then I still have a 10k buffer to at least finance the move. We are not rich, but we save 1000-1500€ monthly, practically saving an entire salary. Therefore, we want to finance a house with a mortgage loan, but the qualitatively better house was rejected because, according to the bank (Münchener Hypothekenbank), it would be worth much less than the seller demands. Therefore, I looked for Plan B to at least get the Plan B house. After that, I could have taken care of all relevant documents needed for a modernization financing. But I just would have a house first