In cities where housing is in short supply like New York and San Francisco, permanent residents are understandably upset when their landlords boot them out to use their apartments as mini-hotels. To prove that this is happening, ousted tenants are turning to private detectives who monitor their former apartments as if they were cheating spouses.

While some cities have passed ordinances that limit the number of apartments that one person can rent out on a short-term basis, these local governments simply don’t have the huge staffs that would be needed to inspect and check up on every apartment or room listed on vacation rental sites.

That leaves an opening for another way to enforce existing laws: lawsuits by tenants who believe that they were unfairly evicted to empty more apartments to serve as illegal hotels.

“Unfortunately, or fortunately, depending on how you want to look at it, it’s a decent living in San Francisco right now being an investigator doing these kind of jobs, because here are so many of them,” one private investigator handling vacation rental cases told Bloomberg.

Private eyes sometimes pose as prospective tenants, and sometimes serve as the inspectors that cities wish they were able to deploy, checking furnished apartments for safety violations and hotel-like amenities like tiny soaps.

Airbnb has started to enforce some of cities’ limits and ordinances on vacation rentals, limiting hosts to one home within city limits in New York City and San Francisco. Yet the company also ensured that it wouldn’t be held liable or fined for hosts that use its service to offer infringing spaces.

Instead, maybe it’s up to tenants’ lawyers and their detectives to enforce the rules.

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