The legal age to enter into any contract in the United States is 18, according to Nolo. Because a lease is considered a legal contract, a tenant must be at least 18 to rent a house.
In some cases, a landlord may require a co-signer if the renter is under a certain age. A co-signer or guarantor is typically a parent or trusted relative or friend who guarantees the lease of the home in case the renter fails to pay his or her rent. If the renter is under the age of 18, a guarantor is typically required, since the potential tenant most likely does not have an established credit history. According to U.S. News, it is crucial that a co-signer understands that if the tenant is not able to pay the rent, then he or she will be responsible for the expenses.