23/10/2026
Renting a spare room or a granny flat can help with the mortgage. It can also cost you part of your main residence CGT exemption when you sell.
The taxable share is worked out by floor area and time, and if you start renting years after moving in, you are generally treated as buying the home at its market value on that date. Family granny flat arrangements have their own exemption, but it only covers the arrangement itself, not the later sale.
How it works and what to do first: https://www.ftconsultants.com.au/renting-part-of-your-home-granny-flat-cgt/