House construction financing - What is possible and realistic for us?

Most of the time, when comparing existing buildings to new constructions in terms of size, location, and features, apples are compared to oranges. The floor plan is always the same, trying to sweet-talk a new building that you can hardly afford.

In this forum, I often get the feeling that there is another currency in Germany. A kind of Southern Euro, like the East Mark back then. Exchange to Northern Euro one to two.

Unfortunately, that is indeed the case. But unfortunately, the salaries are not 1:2. In the Rhine-Main area, it is very difficult to get a plot of land, and then it is outrageously expensive (unless you want to wave at the airplanes from home), or you really live somewhere in the middle of nowhere and still pay 300 euros/sqm. I am also surprised at some comments like "nothing works for me under 500 sqm," I would like to see them here, they would already be very happy with 300 sqm.

650k without reason?

The statements referred to 650 including land and ancillary construction costs. And that is indeed becoming more and more of a challenge for 180sqm on 650sqm in southern Germany in a reasonable location. (Although not impossible, if I should also give an assessment...)

Yes, definitely....

Make your own experiences. But feel free to report here in a few years about the sums actually paid. When I look at my first posts from 2013 here and read the figures (which I once had in mind) and now see where we have ended up... I think well x2

Make your own experiences. But feel free to report here in a few years about the actual amounts paid. When I look at my first posts from 2013 here and read the numbers (that I once had in mind) and now see where we have ended up... I think about double

Well, not everyone sinks over 100k into the outdoor facilities.
So this will probably have continued in the other trades for you...

The message is still correct, even though Steffen's cost development probably has other backgrounds.

It is always more expensive than initially thought. You are simply a "beginner" in this complex topic and cannot immediately grasp everything.
And by that I don't mean late escalations that hit again.