Colleen Grucella had never used Airbnb before, not even as a guest. Neither had her fiance. But on Wednesday they became first-time hosts for the short-term-rental website, welcoming two staffers from the Bernie Sanders campaign into their South Philadelphia home.

Grucella said the roughly $400 they made will help with their wedding plans for the fall. But "it wasn't about money per se," she said. "I wanted people to be able to experience the event."

Grucella, 28, joined hundreds of new Airbnb hosts in the Philadelphia area during the Democratic National Convention. The online service lets people list their homes or spare rooms for rent. Hosts can choose their per-night price, the amenities they offer, the stringency of their cancellation policy, and the dates they are open. Airbnb charges hosts 3 percent of each reservation's subtotal.

"We thought about offering the whole house and leaving town for that week, but I didn't really want to do that," said Grucella, echoing concerns that others have about the service. "So we just listed our bedroom."

"I had two cancellations because they found hotel rooms, so it seems like people prefer hotels over Airbnb."

Like Grucella, one-quarter of all Philadelphia-area hosts for this week's DNC were new to the role. And their homes were in demand. Airbnb estimated its Philadelphia partners would welcome over 5,000 guests for the convention, a 250 percent jump from a typical week.

"We can provide the necessary elasticity in numbers when cities host big events," said Christopher Nulty, Airbnb spokesman.

On the site before the convention, many Philadelphia-area listings had a "NEW" label next to them. And lots had "DNC" in the title, making them likelier to capture people who searched for DNC accommodations.

The eight-year-old private company is said to be valued at about $30 billion. Though specific numbers remain confidential, Wharton School senior fellow Barry Libert said its rapid growth continues to drive massive investment.

"It's a great business; it's unbelievable," Libert said. "I can now, as a customer on a platform, become a supplier of what I personally have. And because the world is changing, I can have more flexibility and freedom. . . . It's like Instagram for housing."

Long-term, Airbnb "is not good news for hotels," Libert said. "The old days, you had to stay at very limited options, now you can stay at Airbnb homes for the same price."

Or maybe less. The average rate for a hotel in Center City last year was $182 a night, said Ed Grose, executive director of the Greater Philadelphia Hotel Association - compared with $100 a night for Airbnb during the convention, the firm maintained.

Grose said he did not yet have numbers, but believes hotels had a very successful week.

"We were virtually sold out in Center City, and imagine the rates were pretty high," he said.

Jumoke Dada of Philadelphia also made a new listing on Airbnb for the convention, a room in her townhouse for just under the average price. But she soon saw huge demand beyond the one-bedroom suite. So she set up an air mattress and listed that, calling it a "DNC special." "People have been biting," Dada said. She expected to make over $1,000 by the time everyone leaves Saturday.