Try to find a small independent “guy” that can vacuum out the old Freon and replace just the outside unit and install the new Freon. 

Hi John,I am getting a Ring Camera installed (lesson learned there). 

You charge them for the stand, and professional installation, and they leave the mounts when they move out or pay for your removal.

You could also look into installing a pump to increase the pressure in the pipes.

That being said, if this is a nice neighborhood, I would have the screen door installed.

I recently had our PM buy and install new smoke alarms.

But lighting and Room receptacles are ran using Knob  and Tube, i am having AFCI breakers installed on all runs with Knob and Tube.

They came back saying it needs to be approved (which is fine) but now also want to potentially charge $6k for a portion of the lot that is owned by the community to install rocks/gravel. 

Appreciation there is low, rents are low, and assuming maintenance as a fixed cost (for example, a hot water heater costs $450 from Lowes in Allentown, $450 from Lowes in Scranton, installation takes the same time, and labor costs aren't all that different), the ROI isn't great.

New central AC with heat was installed in all four units each time an existing tenant moved out.