The goal of making AirBNB rentals a crime in the first place is to reduce the number of them. I claim it would be a more effective deterrent to go after the ten

The goal of making AirBNB rentals a crime in the first place is to reduce the number of them. I claim it would be a more effective deterrent to go after the tenants who are profiting, rather than the homeowners who already have no incentives to allow it. The article mentions the tenant stole some furniture that ended up on two additional listings. If the city went after them, they can nab a serial offender which seems more valuable for reducing the number of illegal AirBNB listings than going after an unaware homeowner. The contract wouldn't be an obligation of the city, but rather a useful tool to enforce the law.