I don't see mold or anything to alarming.

  Get a simplisafe alarm (i am not associated) and put the base station where it can be seen thru a window, it glows in an obvious "I am enabled" kind of way.

Keep or Remove Brinks Alarm System in ~95k Flip House: We believe we should remove it while we are paint prepping as it may represent a hassle to potential buyers, but it seems to be a fully functional and not too old Alarm system, that would just need to have the monthly service connected with the Vendor. 

The title officer is responsible for filling each paper the proper party, dispersing funds to the proper accounts and sounding the alarm when the deal is complete.

Just wondering what would happen if they (the owners) in the absence of the "guest" entered the property, changed the locks (just like the "guest" did), threw out all his stuff to the curb and put some really good home alarm system...

(ie, tenants are responsible for changing water filter elements, fridge filters, furnace filters and smoke alarm batteries.)

Granted, a smart thief could plan ahead if they know its the security system that’s plugged in... but you’d probably also at least get a power outage and low battery notifications. 

Taking these measures prevented another theft, though it is possible the thief was just all stocked up on water heaters ;).

Put it in and let the tenant pay for the monitoring if they want to.It will still function as an alarm system even with out monitoring.

If I were to invest in real estate property again, I would still have an issue with the process, in that I would have to monitor Property Management company like a little child or a thief in the night.