The 30 day line is real in the sense that most short term rental ordinances are written with a stay-length threshold, and that threshold is very often 30 days or one month. Stays under it get the permit requirements, the caps, the registration, sometimes the outright bans. Stays at or over it are usually treated as regular tenancy. That's why mid-term rental means furnished stays of roughly 30 to 90 days, and why operators guard the 30 day minimum so carefully.
What you can't do is assume your city uses that number. Some use 28 days, some use 31, and a handful define a short term rental by whether the unit is furnished or advertised nightly rather than by length of stay at all. This varies by city and state, so you need to read your own ordinance or have a local attorney read it, and get the answer in writing rather than from a forum.
The piece people miss when they focus on the ordinance: once a stay crosses into ordinary tenancy, your tenant may pick up tenant protections under state landlord-tenant law. Eviction process, notice periods, security deposit limits. A guest you could ask to leave at 10am under a hotel-style booking becomes someone you have to go through a legal process to remove. That's a fair trade for the regulatory calm, and it's the reason screening a 60 day furnished tenant matters more than people expect.
So yes, four tenants a year instead of forty. Also four screenings a year that actually count.
