Ryan Trefethen (left) from LA enjoys trailing his host around town to experience life like a local.

"Couchsurfing is definitely the best choice for low-budget travelers," said Tilman Resch, a 24-year-old postgraduate student from Germany who spent six nights on Su's sofa.

"From the moment I landed in China, I spent just 1,600 yuan ($258) for my recent 10-day trip to Beijing and Shanghai - and 1,100 yuan of that went on train tickets."

In China, the culture of couchsurfing is growing as more young people seek out adventure on a shoestring.

Li Xuanran from Zhengzhou, Henan province decided to take a gap year so she could couchsurf her way along China's prosperous east coast.

"I wanted to prove to myself that I was independent and ready to face any challenges society will throw at me," she said.

One of her hosts was 26-year-old Gu Wenxuan, who works as an agent for local punk bands in Shanghai. He receives dozens of requests from Chinese applicants each day and said he has seen interest spike in the last two years.

"I don't do it make friends. I already have enough of those," he said. "I just want to lend a hand to fellow travelers and those in need."

For veteran couchsurfers like Ryan Trefethen of Los Angeles, it serves as a shortcut to free local tour guides.