Accessory Dwelling Unit, simply called ADU, refers to a second dwelling unit on a single residential family property. These additional units can be constructed on practically any housing property. It is important to mention that since these two structures are situated on a single property, they have to be sold together whenever the homeowner decides to sell off his property. This significantly increases the value of the property. Over the years, there have been different names given to these additional homes. This includes granny flat, carriage house, tiny house, garden cottage, guest house, casita, studio apartment, in-law suite, among others.