Last time I was in Germany I saw what appeared to be homeless children
It's… like… not that simple.
No, I'm not stupid or lying.
And yes, it's true. It's just that this housing is not in Berlin.
That said, an idea has come to mind: UK and Italy have had schemes where a home can be purchased for £1/€1 under the condition the new owner repairs them (the repairs would cost 20-150k). Given some of the really bad stock I've seen in some searches, this may be a good idea for Germany too.
And yes, you can find even cheaper apartments.