It is detective's work.

Certainly up-coming neighborhoods can be detected, but with what I know they are lagging indicators.

A detective determined that the 3 teenagers and the relative who reached out via Facebook are all related to Gang activity. 

Our sump pump - power/ water detection monitor has been a big hit which might be of interest to homeowners in your area.I'd be happy to send you some more info or jump on a call!

I'd then think about re-structuring your business to something more specialized, such as leak detection as an example   I'm not really sure what specialties there are in plumbing   Find yourself a good guy to work for you.  

This goes more quickly if the scanners can detect which file your documents belong to.

your a good detective :)

Few weeks ago, a leak was detected in the condo bathroom underneath my condo (I bought the condo 2 months ago and is rented out).

Change your frame of reference.If the owner was a long-lost relative who has a rare blood type that you desperately need for a transfusion in order to stay alive, you'll get both creative and resourceful.The tenacious detective will use online skip-tracing techniques and offline methods.

If you are on a tight budget, door knocking and/or driving for dollars may be a more effective means ... you're looking for beat up properties with equity and can use detective work on the ground to gather further info on the situation ... if you can't set an appointment directly with the owners in person, you can follow up on promising leads from that via mailers, and that would likely be a much smaller (less expensive, but higher quality) list.