How to find the "average days to rent" in a particular area?

[Naga A.]

I know you can find rent comps rentometer.com and other websites, but how can you find out how long it takes on average for you to rent out a property in a paticular area?

Other than asking a property management company and driving around neighborhood for "for rent" signs (I am an out of state investor, so the latter method is not possible), is there any way (or any website) to find the information?

Even if the demographic data shows a low vacancy rate for a particular area, buying a house in that area does not make sense, if there is very few people looking for a rental house. Thanks,