Before you think you can get vacancies eliminated, read this

http://www.forbes.com/2009/07/23/vacancy-homes-rents-lifestyle-real-estate-vacancy-cities_slide.html

 This is a pretty interesting article. If you are buying in NY , Tucson, Jacsonville and some others, you should see where it ranks. This article takes the owner homes that are now vacant as well as the rentals that are vacant. Some of these areas would be difficult to correct the emptying out of occupants. Be careful and do some research. Good luck. Rich