Harkness began renting out his family home for $450 per night, but now makes $600 per night and his boat for $650.
"I know exactly what the yield works out to be with the rentals I get and I found out that the actual yield would jump up quite dramatically using Airbnb, which starts to raise the question 'Should I rent this property full time through Airbnb?', but I haven't got to that point yet," he said.
Grey Lynn resident and Airbnb user Laura Tullok said she hopes people don't use the service that way.
"That's an example of people moving away from that original idea of sharing your space, having strangers come in, getting to know strangers and doing a bit of a cultural and knowledge and everything exchange," Tullock said.
"Now there are many, many people in Grey Lynn putting up their houses for rent."
Tullock, who runs a private Airbnb support group on Facebook, said she thinks the spirit of Airbnb has been lost.
"There's more people in the group who are concerned with making the dollar, or maximising their profit, rather than what Airbnb started off being which is sharing in the spirit of the sharing economy."
It's people with existing family homes who make up the vast majority of Airbnb users, Harkness said.
"It's actually creating supply which previously didn't exist," he said.
