Hard to believe so much money has been invested in this business.

The online dog-sitting community DogVacay just raised $25 million, bringing its total venture funding to $47 million, Fortune reports.

The so-called "Airbnb for dogs" got the Series B1 round of funding from Omers Ventures and GSV Capital, as well as existing investors including Science Inc., First Round Capital, Benchmark, Foundation Capital, and DAG Ventures, according to Fortune. 

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The company won't reveal details on its revenues, though CEO Aaron Hirschhorn told CNBC in August that the site's bookings had grown 10-fold in 2013.

"DogVacay has paid out millions of dollars to its 11,000 hosts across more than 2,500 cities in the U.S. and Canada," DogVacay spokeswoman Corinna Pieloch told Business Insider. "The U.S. pet services market is $11 billion annually and surprisingly there are 78 million dogs in the U.S. – more dogs than there are kids (73 million)."

According to the American Pet Products Association, Americans spent an estimated $55 billion on their pets in 2013, including an average $327 annually on boarding.

DogVacay keeps 15% of hosts' charges, which range from $20 to $70 per night for boarding in New York City. Hosts can also offer dog walking, cat sitting, grooming and other services through the website. 

Some have questioned whether the company can generate enough revenue to survive.