is in your low value asset rust belt mid west.. were your dealing with 10 to 20k houses in the first place. what value will they have if its some huge number to remediate  these items, I can  see a scenario were houses will just crumble to dust as they don't have enough physical and economic life in them.. 

Atlan - you of course need to understand the economics of any deal and the location. 

Seminole Heights is an area that I can tell you off the top of my head that is experiencing some gentrification.Here's a few links that you might find useful:http://www.tampaedc.com/http://www.tampagov.net/economic-and-urban-development/programs/community-redevelopment-areas

As a rule seniors tend to take much better care of their homes and come from a much more stable and predictable socio economic strata.

I don't know the rules in your area, but you need to know them inside and out.I see 5% for physical vacancy, but what about economic vacancy?  

So long as you know the risks associated with your decision, then feel free to go for it.Keep in mind, cities are adaptable when it pertains to ecological or economic disasters.

There are too many investors in our area who are buying substandard housing, just to prey on low income elderly enters, people with disabilities, and families who are economically disadvantaged.  

Max Shepherdson You'll often find that economics on those areas are great on paper but getting a good tenant is extremely difficult.

This certainly points to where next to expect economic prosperity with respect to real estste investment.

@Pedro Oliva Call the city economic development office for this type of info.