A multi-family, 2-4 unit property is a type of real estate that contains two to four separate living units within one building. The units are separated by walls and have separate entrances, kitchens, and bathrooms but may share common spaces like yards or driveways. The properties are often referred to as duplexes, triplexes, or fourplexes. In Chicago, we call them 2, 3, or 4 flats. No matter what you call them, one person owns the property, and each unit's rent helps the owner pay the mortgage, tax, insurance, and other expenses.