Houses with granny flats are all the rage right now, and for good reasons. On average, an ADU can add over 30% to the real estate market value of listed properties. Plus, since they can be rented out for significant profits, granny flats are considered one of the safest real estate investments accessible to typical Aussie families. Sure, they are not exactly cheap. But, they are significantly more affordable than constructing a new primary dwelling, and the paperwork required to start construction, at least in NSW, is simplified.