Exactly for that reason, you should check the numbers and maybe only finance for 10 years now. Or 15? Is 15 even possible?
Yes, we did 15.
If you can no longer pay the annuity, then – after maybe some begging letters to the bank – everything still goes to the bank anyway? (like in a casino).
As far as I know, the property would then rather go into foreclosure. This misconception that "the house belongs to the bank" just because they financed it is not true. If you can no longer pay your installments and also fail to negotiate with the bank, and the place really gets auctioned off, then the proceeds from the auction are still yours. Probably minus costs and procedural fees and whatever – certainly not the ideal way. But if the auction brings in more than you owe the bank, then the little house belongs to the new owner, and you have to find another place to live, but whatever is left over after the bank is satisfied is still yours.
Just the other way around: if the auction brings in less than you owe the bank, then the house is gone and you still have a bunch of debt to the bank. There was a very interesting documentary by WDR about this, about a somewhat naive family with a chess bookstore. I found it very exciting and also very ironic – how someone who sells chess books can only have a foresight from 12 to midday, that was pretty crazy. o_O
Then you are not familiar with current purchase prices. In big cities, you start around 4-5,000€ per sqm for decent locations in new builds.
I already said that I’m not familiar with that (somewhat metaphorically) in the half-sentence behind that, which you didn’t quote. :D