Really competitive pricing, and their electricians are super knowledgeable and do great work.For HVAC, Standard Heating and AC have done quality work on an AC installation, as well as servicing multiple furnaces at my properties.I don't have a good rec on a plumber in the area - all of the outfits in the twin cities I've contacted that have more than 2 employees seem to not want to touch small/medium-sized jobs, and overbid pretty aggressively as a result.  

At my peak had 27 electricians, the last 2 just retired.

Someone pointed out that I call a plumber or electrician when one of my rentals has  issues and I don't try to fix it myself. 

Other REIAs also.Get a list of subs for the trades;  a handyman (or 2) a plumber, electrician, roofer, flooring, painter....   

Have an electrician install sub meters for all the units 

If you look into this option my electrician told me the specific panels and meters I needed and recommended I buy them on EBay where there is at least one electrical supply company that sells brand new electrical equipment at a significantly discounted rate.

The carpet guy rescheduled for 2 weeks out and the electrician for 3 weeks . 

Get to know people in the various trades (plumbers, electricians, carpenters, painters, siding installers.)

I have money to invest and I have some experience with construction as I have worked as an electrician for 3 years, general construction for 1 year and currently doing all of the rehab for my primary residence.

Even with a dozen properties I might need a plumber twice a year, an electrician once, and a handyman a few times  not often enough to be remembered or get priority service  They raise rents faster and higher than I ever would, this alone virtually pays their 8% management fee and $300 new tenant acquisition fee.