Once a rental unit is occupied by a tenant, the landlord or property manager cannot enter the unit at will. Most states give landlords the right to enter their rental property—but only under specified circumstances, such as to make repairs.
Except in cases of emergency, state laws usually require landlords to provide reasonable notice of entry (typically 24 hours). It is considered an invasion of privacy for a landlord to enter the premises just to check up on a tenant. If a landlord does this often, despite tenant requests to stop, the tenant may be able to break the lease and move out, or even sue the landlord for money damages (depending on the situation).