Quote from @Aaron Wolman: I would call the companies (gas/water/electric) to get estimates, or an estimator out there.

@Alecia Loveless is correct--tenants need access 24/7 to their electric service panel, water and heat, assuming those are individual utilities for each unit. 

We have had a pipe burst during the cold winter months, the roof needed to be replaced (thankfully covered by our insurance), and some issues with electrical, which hasn't been majorly updated since it was built in 1973. 

They don't communicate well, don't take responsibility for their actions, do not clean or maintain homes well, and will shaft you when it's time to leave.Other than that, it's a pretty good system.

My husband did 90% of the work himself, only using contractors for large electrical, plumbing, and construction projects.

As Plano is a pretty nice clean cut buttoned up type of community they don't seem to have a lot of tolerance even for just a few bad apples.Dallas is considering a ban. 

I have two options 6.625% 30 year or 6.15% 15 yearI want to invest aggressively in the near future on more propertiesThe loan is only $110k and the monthly payment for 15 year is $563 and $750I will earn 2-3k a month in gross rental revenueThe property is in a declining population areaRecently rennovated, and all major things were relatively recently improved such as plumbing, the roof, a/c, electric, etc.Will require a lot of management as it is rent by the room so I may switch to a normal rental after 10 yearsI'm trying to find what will mathematically net me the most money in the long run.

Electric: is the easiest to split, but may require holes cut in walls to separate the units.Gas: gas lines aren't as flexible as wires, but it can usually be done affordably.Water: most cities will NOT install additional water meters on a property.

He does not want to deal with the headache of tenants cleaning or any thing to do with STR.

That will probably be your best bet, to buy a fixer and get it cleaned up and then rent it out.Best wishes and good luck with your endeavors.