ADUs (accessory dwelling units) also known as "granny units," "cottages," "casitas" and "in-law quarters," have become increasingly popular in California communities, especially those with high home prices and scarce land to build on.
The preferred term to use in real estate is ADU, as that is what the city planners, inspectors and related government agencies and appraisers use.
Today's ADUs are either detached from the main home, or attached to the main residence (also known as a Junior ADU). A detached ADU will be larger than a junior ADU, and will have its own entrance, sleeping, living, kitchen and bath facilities. Conversely, a Junior ADU is smaller (usually 500 sq ft or less), and located entirely within the interior of the main home. It must have its own entrance, and efficiency kitchen facilities. It may have its own bathroom, but it could instead share one with the main home.
The primary reasons that ADUs are built today are to rent out for income, or to house a friend or family member, such as a grown kid or a widowed senior. Some who find they no longer need as much space, move into the ADU and rent out the larger primary home. Building and utilizing an ADU can be a cost-effective means to help alleviate housing shortages.