It's not uncommon in the more expensive German cities as Munich to do a flat sharing even after you finished your studies. You often did a flat sharing when you studied, so you often are already used to the situation. On the other hand living space is too expensive to be able to afford (even renting) if you don't have a really good paying job.

But perhaps this is a different mentality between US and Germany.

Are you talking about married couples taking different bedrooms in one apartment? Or single individuals (not living as couples) taking different bedrooms in one apartment?

Yes, we do a lot of roommate shares here in the US; I lived in about 7 of them through my 20's. But I didn't live with my wife in a room share. I'm now married and I live with my wife, and we are effectively rent-sharers now.

It's still not enough to have a 20% cash savings rate, much of what would be saved as cash instead pays debt (mostly college debt + debt originating from emergencies/unemployment). But we almost certainly couldn't afford a local property of any type, save a studio apartment on the outskirts of the city, with a 20% savings rate over the next 5 years. And part of this has to do with down-payment financing arrangements nearly always losing out to deals paid in cash on-the-spot. (Indeed, there are people roaming the streets with certified checks from $800,000 - $2,000,000 who are viewing new-to-market properties daily)

> Are you talking about married couples taking different bedrooms in one apartment? Or single individuals (not living as couples) taking different bedrooms in one apartment?

I've seen both (OK, they were not married, but in a commited relationship), where of course the latter case is more common.