Renting out a self-contained area while living upstairs yourself?

I watched Love it or List It Australia where one of the houses that was being shown in Brisbane (Camp Hill) had a self-contained area downstairs and the agent mentioned it could be rented for some extra income, or words to that effect.

I know in BCC area you cannot legally rent out different areas separately to two different sets of tenants, but I'm guessing as long as the you (the owners) are living upstairs, you could rent out the self-contained area downstairs (or a granny flat) and as long as the income was added to the other taxable income, it would be ok?

Is it legal to rent out a granny flat or self-contained area in your own home if you also live there, as long as you declare the income?

Is it the same as renting out a room in your own house where the tenant uses your kitchen and bathroom, or are the rules and laws different because it is self-contained (or a granny flat)?

Or is it not allowed (legally) in BCC area?