But if I were to purchase a firearm and concealed carry license and training for the purpose of self defense, without going into the politics, could I tax deduct this expense? 

California required a concealed weapon permit but my belief was I would rather be a concealed weapons violator then a dead non-violator. 

That closet full of stuff could be concealing a roof or plumbing leak, for instance, and we want to handle that in an empty unit.

How do you feel about carrying concealed?

As @George C. illustrated, sometimes trying to conceal or blend-in the cover over the breaker panel is best.  

Inspections are almost never invasive and the plumbing is mostly concealed by this black mesh cover over the insulation in MANU's.Here you can see the PB piping, but not if it is connected to anythingHere's the connection to the city supply.The big question is if the inspector has experience with Manu's.  

But it was only sent to agent (perhaps to keep things concealed?)

I have priced out shaker mdf paintable doors and drawers with concealed hinges for $700. 

I don't know much at this point other than what NY Times wrote about in this article THE PRESIDENT’S TAXES - LONG-CONCEALED RECORDS SHOW TRUMP’S CHRONIC LOSSES AND YEARS OF TAX AVOIDANCE and the (HWMC) House Ways and Means Committee report. 

Concealed carry for realtors nationwide??