The Washington Post has mapped over 52,000 homicides across the United States. (I haven't extensively investigaged the geographic scope of their investigation---but it sounds like an interesting statistic to know about---and the article covers the largest 50 cities).
What they have found is that in certain neighborhoods murder is quite common---but arrests are very uncommon.
The article starts off by mentioning a homicide occurring in a 12 block area of North Omaha---where murders are typically NEVER solved.
My suggestion is that this is one way to identify a war zone type neighborhood. Who even knew that they would exist to any great extent in Omaha?
But, as the article mentions:
"In Omaha, police made an arrest in nearly 60 percent of homicides across the city. But the 12-block area where Dickson was killed saw an arrest in just 15 percent of its homicides."
I would consult the website before investing in cities like Detroit, Baltimore, etc---that have notoriously high crime rates. The fact that a neighborhood has an above average crime rate----when coupled with information like this---ought to be enough to dissuade any investments.
They have maps for San Francisco, Kansas City and Boston---it's rather astonishing that even an upscale city like SF has neighborhoods where crimes go unsolved---but you can see concentrated areas of unsolved murders---where no one is even arrested---so it apparently is true.
They mention maps of other cities that have a low frequency of arrests----or a high frequency of arrests---or a lot of different crime related statistics.
The other reality----in a war zone type neighborhood with alot of rentals----are how many of the residents will move away every year----so that, any witnesses who may have personal knowledge to the crime are quickly moving away. So, unlike a homeowner occupied area---the clock on solving the crime is ticking.