Just like a 'Dual Occupancy', 'Auxiliary Units' and 'Secondary Dwellings' will have a different meaning depending on which state you are investing in and which council you are dealing with. For the sake of this description a house with a connected ancillary dwelling is known as a 'Secondary Dwelling'. It is designed to be tenanted by one family group, with the ancillary dwelling usually occupied by elderly family members or young adults who need some extra privacy. Cultural preferences can be an important determinant as to whether this type of investment is highly desirable in the marketplace. In the right location you can earn a substantial rental premium or resale value. However seeing these dwellings are uncommon and there are not many comparative sales in the market, valuations can be quite inaccurate.