For Allison and Dave Shuttleworth, Airbnb has been a financial saviour. When Mr Shuttleworth lost his job at a hospital last year, the income from renting out the spare room in their house in San Francisco through the online rental site replaced his salary.
The year before, the side job covered three rounds of in vitro fertilisation, at $15,000 each. They are now considering saving up for another round. For Ms Shuttleworth, who works as an emergency room nurse in her day job, the extra cash has not been easy money.
She or her husband gives every guest a 45-minute introduction to the house and the city, maps out bus routes, lays out plush dressing gowns and chocolates and cooks a hot breakfast every morning.