Housing starts is an economic indicator that reflects the number of privately owned new houses (technically housing units) on which construction has been started in a given period. These data are divided into three types: single-family houses, townhouses or small condos, and apartment buildings with five or more units.
Each apartment unit is considered a single start. The construction of a 30-unit apartment building is counted as 30 housing starts.
References
Housing starts Wikipedia(Text) CC BY-SA