However my company was hired to install windows on one of her properties and after the work was completed I got nothing but radio silence.

They aren't installing a meth lab, it's a rabbit. 

You could always use those to prove they were smoking up; with that proof you can either move to evict or simply hold security and at least have some sort of proof.If you install a marijuana smoke detector I wouldn't even tell them what it is (aside from a smoke detector) as they might try and disable it.

Install new tar paper, shingles as well as vent as per instructions.If this is the first experience you've had with repairing roofs I would definitely consider having someone do this for you.

We’re getting a small shopping center installed supposedly by the end of the year (Marshall’s, Tractor Supply, Grocery Outlet) plus investments in a second “downtown” strip. 

You would add value to the unit if you could somehow install a window.

Additionally, the costs on installing parking meters please?

House is rented out regularly but also has a 2nd homesite that has a septic installed & perked for 2 Bed.

I just recently saw a similar post asking if installing PickleBall courts added to ROI.  

I just installed a whole kitchen of IKEA cabinets, and they are farrrrr superior to the lower and even some of the mid level cabinets offered by Home Depot and Lowes.The downside is you have to assemble then, but they are much sturdier than the other big box store cabinets.