The local police department is also involved in the online discussion because they know that keeping out deadbeat troublemakers reduces crime.

I'd call the non-emergency line and let the police handle it. 

Since Dallas is several hundred or 1000 police officers short, don't expect any service on thefts like this. 

One tenant heard gunshots on a regular basis, and even saved a neighbor that had been shot in the middle of the night and lay bleeding in the street until police came. 

That's a part of the city's police force that tracks how many police calls are originating from a particular property, so if the tenants are moving from one of those they may bring the problem along to your property.

So, before I take any action in a case like that I want a police report or something irrefutable such as a video.

Everyone really breaks the zoning laws in this area - the police don't really care - they are mostly antiquated.

The City of Merced Police Dept participates in a pretty cool online tool called crimemapping.com.  

I know the guy who owns the electrical business, almost all they do is run around changing out lights at $100 a pop plus the material costs.The market is much different, generally turn over is higher, tenant income is lower, with higher population concentrations you'll have more police calls, tenant disputes and higher admin costs per unit.

I would look up local police departments for crime rate and greatschools.org for school ratings.