How to know if a location will attract renters?

[Vincent DeAngelis]

Is a spot with a lot of rentals available considered a good spot?  OR is a spot with little/no rentals better because you don't have as much competition?  

The spot I'm looking at with little/no rentals available is only like 10-15 minutes from the spot with a lot of rentals.  I'm not sure if this would be considered "good" or if I should steer clear from areas that historically don't have a large amount of rentals available.  

Any other tips/suggestions on how to determine good rental locations in particular?  Any websites that you've found useful?  

I appreciate all help - Thank you!!!