Most landlords require a deposit when renters move in. The deposit is meant to cover any damage to the property that occurs during the tenant's stay and sometimes may be refunded in whole or part when the tenant moves out.
Laws related to how landlords can use the money collected from deposits and when they have to return unused amounts are governed on the state level. While about half of the states in the United States, as of 2015, set no limit on the amount landlords can ask for, the remaining states set a maximum amount that can be required as a deposit. Other factors that may affect the deposit on a given property include whether the unit is furnished and whether the renter has pets.