What loan amount is realistic for house construction?

Together with my girlfriend, do you find the project feasible?

You are planning a house for about half a million euros, you are young and together you have moderate income. I don't read anything about equity. Oh yes, garage or outdoor facilities are for free? They are not included in your calculation either... a) No bank will go along with this b) Even if a) does not apply, do you find a €2,000-2,500 monthly installment sustainable for you in the long term (also with regard to your desired lifestyle and possible family planning)? So a clear "No" from me.

So the comparable shell construction costs you €220,000 + the costs you mentioned of €100,000 + land + ancillary building costs (€30,000-50,000?). With your income, you can get a loan of around €200,000-250,000, so you could finance the shell construction without land and everything else. Now ask yourself whether that is realistic.

With a rate of 1000 euros/month, I get 300k euros calculated over 30 years - or am I wrong?

I am at about 470k... minus equity, so a volume to finance of 430k. That is absolutely utopian with just your salary and even very, very optimistic for you both together. Plus 50k for the garage and 10-20k for the outdoor facilities. So paving, a small terrace, some topsoil, garden tools, etc. etc.

My advice: look around the existing stock