There is a mechanic on the opposite side of the home as well.

Here is the situation: I recently graduated as a mechanical engineer and got a good job in Huntsville AL.

@Greg Teamann Vacancy rate seems low - I suggest to use a minimum of 8% (unless you have landlording experience and have a make-ready team in place, capable of turning a house in matter of few days).Repairs depend on the age and condition of the house, and the rehab you put at the beginning. 8% sounds about right, if you took care already of most major mechanicals.

Get to know how most buildings are set up mechanically.

Here is the link https://www.boston.gov/departments/new-urban-mechanics/addition-dwelling-unit-pilot

Going forward if the situation arises again(hope not), I would explicitly state that the window units draw more energy and the tenants are responsible for any increases.I don't know what type of AC unit you have, but when you say it's "running rough"...rough as in mechanically or it's just not cooling after the repair?

it's hard to hedge against a specfic industy in momentum, especially when you don't know what the potential mechanism for failure will be  to short against.

The siding has some serious issues and some of the mechanicals are at the end of their lives.

I always ask if they are willing to sign a mechanics lien and make sure they "never get ahead" of me. 

Maybe a mechanics special multifamily in the Valley.