Hi Toni,
This is what I understand from my accountant.
All income from Airbnb must be part of one's IRD income return. I keep good record of all expenses to put against this. I have a council rate loading of 25% for guest accommodation as part of my expenses plus a proportion of my rates say 40%. Electricity at 40% and so on.
If you go over $60,000 income per year on Airbnb then you must register for GST and charge it to guests. If the place you are using (home or unit?) earns $60,000 or more then you must pay 15% of the sale price to the IRD when it is sold.
Regards, Elizabeth