House purchase - split the price 50/50

You write in the original post that she is your "wife." So you are married? Then why separate the funds for the house?

We are married, but each of us is still an individual. Everyone has their own accounts and earns a salary alone. There is an agreement that joint purchases are split as much as possible. If we buy a house, it is a joint purchase where my wife would have the advantage of being able to pay for it from HER inheritance, whether she actually does so is up to her. For me, that is initially just the IF case; she pays in cash and I have to finance my part somehow anyway. Joint financing would be no problem, for which I wouldn't have needed to start a thread. However, one should still consider all possible options. How it ultimately looks depends on the final purchase price and must then be discussed in conclusion.

So I understand marriage differently. Maybe I am old-fashioned.

I think it's good that you want to divide it so fairly. Unfortunately, you also have to plan for the fact that not everything will always be rainbows and sunshine. When we bought our house, my husband brought equity, I did not. We are paying off the loan together, according to the purchase contract he owns more of the house.

If there are no further agreements or [Ehevertrag], then the community of accrued gains already takes into account inheritances and assets of either party before the marriage.

My wife and I looked at it today and it was approved by my wife. I lived in this half of the house as a small child and was already roughly familiar with it. We have decided that we want to buy it. We also have the assurance that we will get it if we want it. I will give the confirmation in the next few days. Soon it will go into price negotiations, which should not be too difficult. When the price is settled, I will certainly be able to provide more precise numbers to ask for your opinion on them. Many thanks already for all the responses so far.

Congratulations on the decision to buy the house!
And yet I want to mention:

My wife (25) and I (27) split all shared expenses as evenly as possible 50/50. Taking turns with the weekly shopping, rent, etc.
That's how it should be with the house purchase, too

Apparently, everyone or almost everyone somehow overlooked this with the mentioned issue.

Everyone has their own accounts and receives their own salary. There is an agreement that joint purchases are split as evenly as possible. So if we buy a house, it is a joint purchase

It can stay that way. Nevertheless, you should also deal with financial matters within the marriage insofar as they contribute to togetherness.
A joint account for joint purchases -> house, loan, etc. should exist. And you don’t have to exaggerate the 50/50 rule, because if someone likes to invite or give, they pay... if someone likes to shop extravagantly for the cooking pot, they pay... the stubborn tallying each time divides the community and makes it brittle.
In this respect, one has to – honestly – not act like Larry with 150,000 as with 400,000.
What do you want to do with your attitude when children arrive? Then this 50/50 tallying no longer works at all.
Therefore: practice now with the house... when a child is here, it is too late.