What States Require
The majority of states require 24 to 48 hours notice to tenants before their units are shown. Some states employ the term "reasonable" or "advance" notice without associating the guideline with a specific time requirement. Many of these states also limit showings to regular business hours or weekdays. The District of Columbia and 20 states have no notice requirement whatsoever.
What Rent Control Requires
While rent control is a local regulation with the purpose of limiting rent increases, often they include other rules pertaining to the tenancy. Some rent ordinances specify the type of notice required before the showing of an occupied unit. In New York City, for example, the Rent Stabilization Law requires the landlord to provide five days written notice before a showing. If there is a conflict between state law, rent control and/or the lease, the most restrictive regulation applies.
What a Lease Says
Although it would be unusual for a lease to contain language regarding unit showing, it is neither unheard of nor inappropriate. A lease cannot be less restrictive than state or local law but can supplement existing law and will stand alone as enforceable if there are no state or local laws on the subject.
What is Reasonable
Regardless of what, if anything, state or local laws require when it comes to notice requirements for showing an occupied unit, no landlord may make excessive visits to the units. In this case the tenants could make a legitimate claim the landlord is violating his "quiet enjoyment" of his home. This is a widely used legal term that ensures tenants are accorded privacy and use of their homes, free from visits that go beyond what is required to run a property management business.