A two- to-four-family property refers to a residential building that contains between two and four units. These units can be apartments, condos or townhouses. These properties are typically classified as multi-family properties, and they can be a good investment opportunity as they provide rental income from multiple units. They are often used as rental properties, but they can also be owner-occupied, with the owner renting out the other units to generate additional income. These properties are also known as multi-family buildings, duplexes, triplexes, or fourplexes.