Sam, the youngest of Hyman and Yetta's sons, joined the family business in 1928. Prior to 1935, HKI specialized in single or twin homes, but in the decade that followed, Sam branched out. They made their first attempt at a new form of housing – the row home. More than 6,000 row homes were built in the Castor Avenue district alone.
In 1938, HKI built its first apartment development, Leiper Street Apartments. Others soon followed at Oxford Court and Jefferson Court. This type of development became a prototype of what is now known as the garden-court apartments in Philadelphia. Apartment Center, the company’s first apartment complex, began in 1940, and was fully completed in 1955.
HKI continued to grow as a major developer of planned communities in Philadelphia and the suburbs, constructing single and twin homes, apartments, stores and shopping centers. In 1960, they completed Green Ridge Farms, luxury single homes at Pine and County Line roads. It was recognized as a model suburban community. They also completed Brentwood Park in Bustleton. More than 600 homes in both developments took place. They also completed final plans for Parkwood Manor, the largest development ever started in Philadelphia by a single homebuilder. The following year, HKI astounded real estate brokers, builders, planners, bankers, and the public, with more than 800 homes started in the ambitious new development.