Regarding the job servicing security systems: I was in installation before another guy and I started their first full time service team. We operated out of the owner's old Ford Country Esquire station wagon (The Blue Goose, as we called it.) The company worked under contract with the property management company, and installed both security systems on every quite in the building as well as card reader access control at the main lobby entrance.
Most everything we did was concealed wire, running fish tapes in suspended ceilings and dropping wires inside the walls at every single suite. I've used a hammer drill to drill holes through all the concrete support pillars in parking garages to run the cable where it needed to go. One old DC building was solid plaster walls, and we used a drill to rout groves in the walls to lay the wires in throughout the entire building to every single suite, then plaster over them. We looked like we had worked in a Lucille Ball bakery episode every afternoon, all covered in plaster dust.
Side story: The systems were controlled and monitored from our Monitoring Center in Rosslyn/Arlington VA. It was all passive for the tenant. We remotely turned on all systems in the entire building overnight, then off again in the morning. This was done via phone lines. When they were digging the METRO subway tunnels in the late 70s, the crew cut through a telephone trunk line. This severed communications with the monitoring center and armed every security system in several entire buildings in the middle of the work day. I remember walking into the Merrill, Lynch, Pierce, Fenner & Smith building on Connecticut Ave. There must have been dozens of sirens going off at the same time, all oscillating at different rates & frequencies. The place sounded like it was sinking into a METRO tunnel. I walked in the lobby to shut the thing down, conspicuous in my non-business attire gray slacks, tool pouch and white shirt with the "John" name tag on it. Fun times.