A Boston tourist got a surprise when she booked a $90 a night Airbnb — in a run-down New York City Housing Authority (NYCHA) housing complex.

Rachel Valerio and her mother were concerned when they unlocked the door of their seventh floor rental and were hit with the smell of gas, according to a report. There was a roach trap near the bed too. When they Googled NYCHA, they felt worse.

NYCHA is the United States' nation's largest public housing system, home to 400,000 low-income residents.

Two highly contentious housing issues collide in New York City: the future of the city's 176,000 crumbling public housing apartments and the proliferation of Airbnb, which has 50,000 listings in the city.

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There are about 177,000 people on the waiting list for a NYCHA apartment; many who have been waiting for years.

NYCHA's official population is about 400,000, but that number doesn't account for residents who are not on the lease. Unofficial estimates, based on trash volume and anecdotal evidence, have pegged the number closer to 600,000.