Construction financing - what can we afford?

Honestly? If I were you, I wouldn’t do it that way. Even with 500k, you can get a really nice house, afford quite a bit on the side, and if necessary, you can pay it off with just one salary. The risks are too high for me, in my opinion, there would be too much remaining debt, and if I start counting on tax refunds? No no... from personal experience: that whole tax refund thing just doesn’t work out during parental leave. Besides, I get the impression that you’re always making it look better than it is. Even if your salary increases, expenses will increase too. No one can say for sure how much real extra money you will have in your pocket in the future. Therefore, I wouldn’t rely on it either.

I assumed the whole time 700K€ for house + land

At just under 900K€ total costs, I would definitely drop out.

one more point. You want to give up a lot in terms of vacation and home holidays (but they also cost money) and offer the children a generous house. But where do I find a child-friendly garden here in these sketches? I am building for 700k and have a huge slope. So playing football etc. is out of the question.........

my 140 sqm mini garden is better off there

At the first post, I thought "no EG, but two civil servants with 5500 net... should work even with a 650k loan." But the issue with the slope makes me doubt. The house is certainly not feasible at these costs (a lot of glass also costs a lot of money)! Counting child benefits and tax refunds, I also see as a big mistake. We have a significantly higher net income and a 500k loan with a total volume of 850-900k. In addition, 100k in savings as a reserve. I consider our loan borderline and I want to reduce it to at least 350k within the first 5 years. Then it’s time to "breathe easy"...

At first post I thought "no self-employed, but two civil servants with 5500 net... should work even with a 650k loan." But the issue with the slope makes me doubt. The house surely cannot be realized at these costs (a lot of glass also costs a lot of money)! Counting child benefits and tax refunds, I also consider it a big mistake. We have a significantly higher net income and 500k loan with a total volume of 850-900k. Plus 100k in savings as a reserve. I consider our loan borderline and want to reduce it to at least 350k within the first 5 years. Then it’s time to "breathe easy"..

but you are your own master. If you give mega gas, more money comes in. That’s more manageable with an employee, civil servant. Don’t think anyone wants to start a side job

where you are your own boss. If you put in a lot, more money comes in. That is more manageable for an employee or civil servant. I don't think anyone wants to start a side job

Conditionally... the other way around: My risk is significantly higher. The civil servant basically has no risk. That speaks in favor of the financing OP. 500k...600k... loan with 5500 net income... I think that is relaxed. For the OP, we are probably talking about a 700k-800k loan.