By installing our own, we remove the wear and tear and damage the tenants do by moving W/Ds in and out and hooking them up wrong (which is common) and using cheap components that cause leaks and destroy floors and walls.

Or should I have Ring cameras installed outside.

Lol.....Maybe I should develop a business model that installs them...for a slight additional fee. 

Instead spoke to my friend that I will pay commission to my realtor-friend, on 16 installments and no interest on it.

You can use a card reader on the coin-op feature to address that, but you are into micro-issues at that point that I wouldn't want to deal with.A proposal: Tenants, installing separately metered water and electric lines that I pay for, then bill you for, will cost me $5,000 (or whatever).

Other small things I do besides leasing, mangement, some maintenance, are installing keypads to doors, programming gate remotes, garage remotes, doing walk throughs, doing walk through videos (15-20 mins move in/move out videos), advertising videos, take care of our website, our portal, fix the gates and cameras when they go out, just like everything you can think of.   

Consider adding motion-detecting floodlights and installing visible CCTV cameras around entry points to deter crime.

Screwing a 4x4 screen into a roof would probably not show up as an "installation". 

or "Could I see where you have installed these units?"

Consider an Installment Sale: By structuring the sale to receive payments over multiple years, you can spread the capital gains tax liability over time, potentially keeping you in a lower tax bracket each year.11.