Airbnb operator Jennifer McConnell with her dog Skipper, in a communal area of her home, in Cambridge, US. [Photo/Agencies]

Airbnb says it is not to blame for spiking housing costs. Only a small percentage of the Cambridge housing stock－about 140 homes or apartments－are rented through its website for more than 172 nights a year, it says. That's Airbnb's estimate for someone who is effectively doing short-term rental as a business.

Interest in renting rooms through Airbnb often jumps during graduation or a big football game, says Will Burns, public policy director for Airbnb.

Visiting scholars and families of college students also fill rooms. In Cambridge, an annual rowing event on the Charles River also creates demand.

In the past 12 months, Airbnb says, there have been 90,000 guest arrivals in Cambridge through its service in the city of about 110,000.

Kirsten Rulf, a 36-year-old research fellow at Harvard Law School, says she used Airbnb for two weeks in August 2015 before finding permanent housing. The small, furnished room in a larger apartment cost her $1,500 for 14 nights, she says.

"For me that was the best option, because hotels are super expensive, especially in August," says Rulf, who hails from Mendig, Germany.

Some institutions, including Boston's Emerson College, have even busted students for trying to rent out dorm rooms.

An agreement on graduate housing at Yale University states that while students are allowed to have guests for short visits, "Guests who pay rent and/or guests found through Airbnb or similar arrangements are prohibited".

In Cambridge, the median rent has soared to a daunting $3,000 a month, according to real estate data provider Zillow. In Boston, which sees its population swell every September when students flock back, the median rent is $2,700.

McConnell, the Cambridge resident who opens her home to Airbnb clients, says she's OK with the city's regulations but isn't thrilled about the inspections. She says she also doesn't fault Airbnb for the city's soaring housing and rental costs.

"The middle-class person has a hard time finding a place," she says. "I don't blame that on Airbnb. People couldn't afford to rent those places anyway."

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