Which of the following is an example of a smaller multi-family unit?

A duplex is indeed an example of a smaller multi-family unit because it typically consists of two separate living units within one building, allowing for two households to share a single structure. This configuration enables the owner or renters to enjoy shared walls and possibly shared entrances, but still maintains distinct living spaces for each unit.

Multi-family units are generally characterized by housing designed to accommodate multiple families or households, and a duplex fits this definition perfectly. It provides the functionality of multi-family living while being smaller in scale compared to larger apartment buildings or complexes. In contrast, other options like high-rise condominiums, commercial apartment complexes, and single-family homes either cater to larger populations or one family, making them less representative of smaller multi-family units.