Property purchase - for 2 people & one falls into a coma?

If you, for example, have a carpool to work, you have already founded a GbR...

Correct. Or if you get married ;-)

A notary can help you in a private law matter. Establishing an operating company is another option. Advice on the type of company is more likely to be given by a clever business or tax consultant. The solutions are then resolved in the shareholder agreement. However, the company should have a recognizable profit intention in the long term, but that can also be solved.

I meant the compulsory portion. Strictly speaking, there is no compulsory portion heir, since the compulsory portion does not refer to the estate (in substance), but only to a financial claim for payment. That is why I used the cumbersome wording.

Oh, so the half of the property is part of the estate along with cash, spoons, etc. And a certain part of that is the compulsory portion. But the parents of one could waive their share of the inheritance portion of the half of the property? Or can one only waive the entire compulsory portion?

No, actually quite different. Let’s simplify the case: A property belongs to 2 people, there is only 1 heir. Either the statutory succession applies and the heir steps into the place of the deceased, thus the co-ownership share is transferred to him and he is then the owner himself. Or there is a will that bequeaths the ownership of the property to the second owner. This gives him the co-ownership share and he is the sole owner. The actual statutory heir now has a compulsory portion claim. He can demand from the testamentary heir half of what would have been granted to him by law. But this claim does not relate to ownership, only to monetary compensation. He can therefore claim money, but not ownership of the property, not even half of the co-ownership share. However, this payment claim can lead, for example, to the property having to be sold if the compulsory portion claim cannot be met from other assets.

You are trying to deal with complicated situations here and lack essential knowledge. Therefore, please heed the advice and seek professional advice on what solutions exist and what advantages and disadvantages are associated with them. Everything else here in the forum is rubbish.