Is building a house currently affordable or should one wait and save?

In the listing there are €65 for donations but €0 for vacation?

From an economic perspective, you should discuss in the medium term whether the person with the better hourly rate (your wife?) should increase to at least 35 hours. Although for "Consultant" the question arises whether that should not automatically be 45+ hours. 40% of net is acceptable if from your perspective there is potential for growth and it will indeed increase. Otherwise, you definitely have to want it.

Well, either the money is enough for the magic triangle: top house in a top location with a top plot, or you have to make compromises somewhere like almost all of us. Either on the small plot, the age of the house, or the location.

In my region the reasonable market is also empty. I would also rent, but there is almost nothing and if there is, then at prices that are outrageous: 130 sqm semi-detached house with equipment from 1990 for €18/sqm, with a rent index of ~€12. And for renovation projects, many are still in the price world of two years ago. The rare newer and/or good offers are only online for a few days.

I would also rent, but there is almost nothing available and if there is, at prices that are outrageous: 130sqm semi-detached house with 1990s fittings for 18€/sqm, with a rental index of ~12€.

But that is normal. You cannot apply a rental index to single-family houses, or there is practically no rental index that specifically lists single-family houses. The prices are simply different than for rental apartments (there is a rental index for the purpose of "apartment"), as the utility value is also completely different.

I'm completely with you. Although the rent index is included, they are on average 1.5-2.5€/sqm higher than for apartments. It's fair, no question, you get "more" for the money. I just find the upper price limit for below-average dumps annoying.

At some point, you have a house where you can live. Your previously good equity is then gone, and you have around 500,000 euros in debt that will probably accompany you for the rest of your life.

In my eyes, you are on the verge of financial collapse with a ridiculous 10,000 euros of equity. I would really feel exposed there. Nothing must go wrong.

So either you keep 100k in reserve and finance correspondingly higher, reduce the construction costs, or save a bit more.
That is good for your nerves and your financial freedom.