Simply going to AirBNB.com & looking at the area, there are a decent amount of listings in the area. Also looking at their calendar availability, the bookings look pretty good. Reading some reviews, the market doesn't seem solely dependent on Churchill Downs. With it being a central location with easy access to downtown/airport/UofL, it's supportable. The common denominator for 'complaints' (though they didn't negatively affect the reviews) was the neighborhood being sketchy. A few hosts include a disclaimer about it on the listing - one said it was a "working class neighborhood", haha.
I'm close to getting a property in the area, just trying to decide whether or not to rent or AirBNB. AirBNB obviously incurs the utilities (including internet...maybe cable/security), property management, and hotel/local taxes that I'm still trying to educate myself on...not to mention the upfront/semi-ongoing furnishing.
