A casita is a small, self-contained dwelling that is detached from the main home but located on the same property. It is also known as an in-law suite, in-law apartment, guest house, carriage house, pool house, or mother-in-law suite. Casitas are typically smaller than the main home on the property, ranging from around 500 to 1500 square feet of living space. They usually have their own bathroom, bedroom or bedrooms, and a kitchen or kitchenette.

Casitas are versatile and can be used for a variety of purposes. They are often used as guest suites, providing a comfortable and private area for visitors to sleep and relax. They can also be used as a dedicated rest and relaxation area, with homeowners designing them with home theaters or other amenities. Additionally, casitas can be used as rental properties, home offices, art or music studios, or homes for aging parents or young adults.

The cost of building a casita depends on various factors, such as the size, design, and amenities included. Typically, a casita should be no larger than about 1200 square feet or half the size of the original home. The cost of building an accessory dwelling unit (ADU), which is the technical term for a casita, typically ranges from $100 to $500 per square foot.