**Rental Unit:** An apartment, house, duplex, condominium, or room that a landlord rents to a tenant to live in. When a tenant uses the rental unit to live in, it is called a "residential rental unit." **Rental Unit:** An apartment, house, duplex, condominium, or room that a landlord rents to a tenant to live in. When a tenant uses the rental unit to live in, it is called a "residential rental unit."