How much remaining debt at 46 is okay?

If the real estate prices fall by then, you still end up with a mountain of debt. Because you have to pay back the loan plus interest to the bank anyway. If you buy the building for 900k and sell it for only 700k after 20 years, you not only have no money left for another apartment but also still owe the bank... or am I mistaken as a layman? Please correct me if that is the case.

A correction? Gladly: In your example, after 20 years you have repaid a lot, and maybe still have a remaining debt of €550,000 with the bank. That is less than the sales proceeds, so no problem at all.

Whoever has their term until 87 and plans to sell the property profitably at the start of retirement has not understood the principle.

Who says there have to be profit increases? Anyone who starts at 47 and brings >50% equity can also finance until 87 or gladly accept a sideways movement until retirement ;)

Well, then I can just keep renting and buy with the equity and the savings accumulated on the side at retirement. It's less stressful.

Well then I can just keep renting and buy at retirement with the equity and savings accumulated on the side. It’s less stressful.

Then please rent a house with over 200 sqm of living space (+ basement, garages, and ancillary rooms) + approx. 1,100 sqm plot in KFW 55 upscale standard within the catchment area of a German metropolis and tell me that I’m doing well with that ;) . The cold rent for such a house is about 8 times my current interest burden (about 3 times above the annuity).

Please think about what you are writing first. That’s actually quite nonsense.

The cold rent for such a house is about 8 times higher than my current interest burden (about 3 times higher than the annuity).

My husband and I would actually have preferred to rent, but based on your assessment, we found that it wouldn't have been worthwhile for us either to rent a house. Maybe it was different once, I don't know.