Airbnb is reportedly standing out from other Silicon Valley "unicorn" startups in one major way: It's profitable, according to Bloomberg. It reached this milestone in the second half of 2016.

The company also expects to remain profitable in 2017, before interest, tax, and amortization, according to the report.

A source close to the company confirmed this to Axios, adding that Airbnb revenue grew more than 80% over 2016. Nearly all of the $3.1 billion the company has raised from investors remains on the balance sheet, says our source.

Why it matters: Large private tech startups with multi-billion dollar valuations like Airbnb, Uber, and Lyft have raised a lot of questions about whether their business models are sustainable and can reach profitability. Currently, neither Uber nor Lyft is turning a profit. These companies also face regulatory challenges in many places around the world, adding to doubts about their ability to survive or even go public.

The story has been updated with additional information.