Electricity bill is fairly high - each unit has window AC units (some units have 2).

Downside is I am unsure if we start changing zoning how much in upgrades will be required by the city such as electrical.

Tenant erected a 12 x 12 outdoor extendable living accommodation shed in the backyard without any permission installed permanent tiles, ran wiring in the shed for lighting, fans, for electrical devices and also for air conditioning.

Some rentals will drag you down in ways that a tenant or buyer cannot perceive value, like plumbing electric, etc.

Scatter the poison bait blocks behind refrigerators, under stoves and in the crawl space of your rental (anywhere kids and pets cannot get to). 

They need to have running water and electricity, etc...

Plumbing and electrical changes have been made where needed as well as boiler and water heater updates to accommodate the extra tenants.

Auto transfer gas&electric into the owner name might have really big bills, besides you don't have to turn gas on in summer.Same with water: if you don't bill tenants for using water - make sure that the owner agrees.

The place needs work on the roof, electric upgraded, HVAC, etc. 

I did extremely conservative estimates as if I would have to replace all plumbing, HVAC, electrical, etc.