correct, but boarding house is not automatic when you have trigger certain threshold of unrelated guest. the application for boarding house requires strict fire safety such as sprinkler installed. It also change some bills such as electricity to commercial which means you pay more, plus insurance for boarding house, and valuation of property considerations because of the class1a to 1b in NSW, etc...
interesting to know other states like they're able to advise how many unrelated guest on state basis, whereas in NSW every council appears to have a different unrelated guest threshold