About two-thirds of the ..families. in the United States live in single-family homes. About a ...quarter of the families live in ..buildings. that have two to four ... floors , or in ..apartments. or other commercial buildings that include apartments.
Large .. cities have more apartment housing than small communities... , because. land.. is scarce and.. expensive. . Small towns and..suburban. areas, where land is .less .. expensive than in city centres, have mostly.. single-family. homes.
Philadelphia and other .cities.. have many . row .. houses. These are usually single-family houses, one or two .stories.. high, standing wall... to wall. A duplex... is a building with two apartments, either .side.. by side with a . single.. wall .. between . them, or one .above.. the other.