Financing a house alone or already building/buying one!?

And if you disregard the factor "expenses"

And additionally, the factor "additional income" is also not considered, but only the net is taken. If one were to say that the annual budget surplus x 20 (= 5 annuity) is really healthy as a rough estimate, then I would agree with it.

Exactly. And if you disregard the factor "expenses," how do you want to determine a loan installment, let alone a credit limit?

I don't want to. You only said that income is irrelevant.

Annual budget surplus x 20 (= 5 annuity)

That's a really helpful statement.

I don't want to. You just said that income is irrelevant.

I didn’t say that. What I wrote was "Ultimately, household income tells you absolutely nothing about debt service capacity and thus creditworthiness."

And that is indeed the case. I like to illustrate with simplified examples:

Family 1:
Household income 8,000 EUR
fixed expenses incl. LHK: 6,000 EUR
= debt service limit: 2,000 EUR

According to your calculation possible loan amount: 8,000 EUR x 108 = 864,000 EUR

Family 2:
Household income 5,000 EUR
fixed expenses incl. LHK: 2,500 EUR
= debt service limit: 2,500 EUR

According to your calculation possible loan amount: 5,000 EUR x 108 = 540,000 EUR

Although Family 2 has better creditworthiness, according to your calculation they get a significantly smaller loan. Family 1, on the other hand, is completely overstretching themselves...

Whatever. Discussion over.

The financier from Kampa told me that yesterday.

I only read Kampa everywhere. Talk to other builders and especially to independent financiers and/or your house bank about the financing.

The hundredfold of the annual net income was also given to us in 2017 by Ing-Diba as a rough guideline for the maximum loan amount.

With 2500 net and no equity... complete risk on your shoulders... I would avoid it.