Once a rental unit is occupied by a tenant, the landlord or property manager cannot enter the unit at will.  It is considered an invasion of privacy for the landlord to enter the premises just to check up on a tenant.  If a landlord does this often, and this action does not stop even after a meeting between the tenant and landlord, the tenant may be able to break the lease and move out.  However, the landlord has a reasonable right of entry and privacy for repair, property inspection, and showing the unit to prospective new tenant, and for emergencies.  Generally, aside from emergencies, the landlord must provide at least 24 hr notice for all other reasons for entry as mentioned earlier.