Bloke that I know up here got done for having 24 students in a 5 bedroom house. Made a killing until Health came in and shut it down, then ATO audited him and found.... Wait for it.... They owed him money!!!
Didn't get the full details, but my understanding was that he had paid to much CGT on a number of occasions, but like I say, didn't get the full story... Could be all hogwash for all I know?
