What loan amount is realistic for house construction?

That's funny. I live very rurally and wouldn't know what could be even a little bit cheaper there. Enlighten us, we are the ignorant ones.

So here "in the countryside" completely different deductibles are calculated and costs for running the cabin, but never mind, everyone already thinks they know better anyway

Then enlighten us. How is the calculation done in the countryside? I’m happy to learn. I also live almost in the countryside and would like to save money like you.

A little calm please with the sarcasm. With all due caution, the original poster wrote;

Net base salary together 3800 euros (both vacation and Christmas bonuses (full 13th salary) not included in the sum)

and

We currently have 40k euros liquid equity - our regular expenses together are 1500-1700 euros per month. (Determined over 14 months, phone, insurance, fuel, rent, etc.) If it matters, we pay 400 euros rent including utilities - which are already included in the 1500-1700 euros.

Theoretically, that leaves 2100 for mortgage, reserves, and additional costs. Let’s say 1500 installment. If he gets 1.2% interest and 3% repayment for a 450k requirement, that fits, just about.

Remaining debt after 15 years then around 225k. Phew, but the OP is only 27 years old.... But with the 450k it really has to stay. Why the girlfriend is not allowed or supposed to be on the land register is still not clarified. Her income must be taken into account by the bank, so probably both will have to sign or the conditions have been calculated for this case, signing alone with 2300 net is absolutely not possible, otherwise the audit at the main branch will shut it down at the latest.

Man, just leave him alone now. You can clearly tell from the mentioned numbers and statements that the OP has no idea at all and is relying on verbal statements from some bankers. Even the desired rate in connection with the loan amount does not fit the acceptance criteria of a regional Volksbank or Sparkasse. A repayment rate close to 1% (which is roughly the case with a 1000€ rate) I believe currently only Ing-Diba accepts. It is also undisputed (as the OP believes) that a house bank has other options to interpret acceptance criteria, but he simply does not meet the requirements for that. There is neither a particularly high income nor significant equity. That means as soon as the information and conditions go to the back office for review, it's over. And the statement that the salary is meager is not quite right. It (2350€) roughly corresponds to the average income in Germany. But for a construction financing of this size, it is not sufficient. That means either it is financed jointly or not at all.

I am in favor of closing here.
?

That both together are much more likely to think about the project is certainly undisputed. With an income of €3800, expenses of €1700 per month, which already include €400 for rent (which will then disappear), there are €2500 left for the dream house. That doesn’t sound so unreasonable. But alone... the bank doesn’t care if one of the strawberries lives in the garden and makes clothes from the wool of their own sheep... you can be as frugal as you like, they just set up their household calculation with the appropriate amounts and that’s it. And with €2350, even as a single person, there isn’t €1500 left after this calculation (and there would also be additional house costs). Repayment... I had an offer with 1.6%, that does exist, and it wasn’t from ING.