.)- Lawyer specializing in landlord tenant law (again you can use your landlord association and get familiar with local laws for bad debt collection, evictions etc)- Police department, do they have community outreach programs that you can join to decrease chances of crime (Cameras and lights are great, but prevention is best!)

While I am not the Topic Police, don't you think you have all been played against each other long enough? 

Only reason I would hesitate to call the cops is because you don't want the neighbors to start associating you property with the police showing up unless you really have to have them there.

As a retired police Commander (30 yrs), I went to Afghanistan embedded with Infantry Brigade Combat Teams (2011 with 45th IBCT, and 2013-2014 with 2nd BCT/101st Airborne) as a consultant on a Dept of Defense contract.

A real estate agent was showing a married couple a home for-sale just outside of Fort Lauderdale, when a gunman barged in and shot and killed the husband before fleeing, police report."

Other than two domestic violence cases, police said narcotics and other illegal activities were involved in some way.

When the police, came he told them that we illegally evicted him.

I should note: it's probably unwise to admit you entered the property, even though you had a good faith belief the place was under contract and you had permission to enter... you may make the actual owner feel very violated and their response could be unpredictable and include things like police (if you're lucky) or buckshot (if you're not.)Tell them your suspicions grew when you noticed Yahoo 2 also had the property "listed" at a much higher price.

We also have a few addendum pages - A page of emergency numbers and non-emergency numbers for local police, fire, utilities.  

When we found boxes of bullets in a house we bought, we donated them to the local police department for their target practice.