Berlin is fairly cheap, cheaper than any other major city in western europe at least. Accommodation prices can vary widely, they can go from as little as 200 euros/months for a studio on the outskirts. I was paying 800 euros/month for a large one-bed flat in fairly central east berlin (P-Berg).
Lots of startups, probably some doing Python, not sure who off the top of my head. Most recruitment in Berlin seems to be done via social networks rather than via job boards, so your best bet might be to get involved with the startup community and get some leads from there.
Do you hire mainly in Germany? I'm curious about working abroad for a while (Australian work holiday, mainly) and am interested in the the opinions on hiring a US citizen.
Lots of startups, probably some doing Python, not sure who off the top of my head. Most recruitment in Berlin seems to be done via social networks rather than via job boards, so your best bet might be to get involved with the startup community and get some leads from there.