Accessory Dwelling Units, also known as ADU, is a detached secondary unit. These units are typically located on a lot that's originally zoned for a Single Family property. In some cases, this additional structure is called an "In-law unit."
Recently, many cities and states have passed laws that permit the construction of an ADU to ease some housing pressures. Property investors can build ADUs without needing to file a Zoning Map Change while being able to rent out an additional unit upon completion.