Airbnb likely had a business plan on how to make money... and they might not have had any profits but they likely had some revenue as soon as they had listings back in '09.
> In February 2008, Nathan Blecharczyk, Chesky's former roommate, joined as the Chief Technology Officer and the third co-founder of the new venture, which they named AirBed & Breakfast. They put together a website that offered short-term living quarters and breakfast for those who were unable to book a hotel in the saturated market. The site Airbedandbreakfast.com officially launched on August 11, 2008. The founders had their first customers in the summer of 2008, during the Industrial Design Conference held by Industrial Designers Society of America, where travelers had a hard time finding lodging in the city.
It wasn't until after that that YC noticed them and invested.