Zweckentfremdungsverbot-Gesetz (ZwVbG)
What it does: Prohibits using residential space for anything other than residential purposes — explicitly catches short-term rentals and serviced/coliving operations under 6 months. Permit can be granted but is heavily restricted in Berlin's tight housing market.
Trigger: Any coliving model with stays under 6 months, any conversion of residential floor area to commercial-style coliving operation, any operation deemed 'tourist-style' by the district.
Fix: Either operate as long-stay residential (6+ months, standard Mietvertrag, residential rent rules apply) or apply for a Zweckentfremdungsgenehmigung — granted only with substantial public-interest justification (often student or worker housing). The 'flex-stay coliving' model is structurally incompatible with Berlin.

