As a rough guideline:
House: 170sqm * 2000€/sqm = 340,000€
Double garage: 30,000€
Basement: 50-70,000€
Additional construction costs: 40,000€
Totals approx. 470,000€ (excluding outdoor facilities and kitchen).
For this amount, depending on the region and provider, you get an average standard. Sometimes better, sometimes worse.
For every 100,000€ loan, you should have at least about 1,000€ income available. For the above amount, that is about 5,000€ per month. Although I wouldn’t feel comfortable with that. In our financing, the ratio is better and otherwise we wouldn’t have built.