This along with your roof should be one of the 1st items explored. 

On my end, I've never asked for one even when there was quite a bit, as I buy investment properties and expect I may have to replace roofs, drywall and other things that might be moldy or contributing to it. 

The foundational items, roofing, HVAC, plumbing and electrical were newer and needed very minimal replacing and updating.

My assumption is that inside installation will cost at least $2000 per home.I will call the local utilities because I think they have a flat rate for doing the outside work.

There's less people buying 2 flats, therefore there's not as much competition to buy.

The roof is from 2008, and I assume the bank is carrying insurance on the property.

https://www.zillow.com/homedetails/114-S-Broadway-St-Toledo-... seller has 'described' it as follows:"The property features a new roof and updated electrical work completed two years ago at a cost of $120,000.

Feel to reach out if you need any contracting or roofing help!

Also, the roof is a barn-style roof, so it starts to slope at about 4ft high.Is there anything I should add or change to suit MTR (and STR in the gaps of no MTR guests)?

You probably don't know about septic systems, foundations, how to look for termite damage, how to know if you need a new roof, how much life is left in the AC, or what it costs (from a contractor) to fix much of anything.