Now have small mortgage, great cash flow and new roof/electric/kitchen.Quality of life is important, however look at who may be your buyers in 20 years.  

slumlord is a pretty harsh term, however, let's say-Its a rough neighborhood (some spray paint and busted windows on various bldgs)-A bunch of 2-4plexes on the block-the living conditions of current tenants is bad (partial electricity, no hot water, holes in windows and walls, rats)-some visible mold on a couple walls-doesn't seem to have had any management/maintenance at allOwner hasn't been able to sell for a few years.   

My properties are in  Naperville, IL  which runs its own electric billing and landlords are responsible for debts left by tenants.  

However the numbers are great & the house had new roof, electric, kitchen.

What I've found is a 36,000 sf mixed-use property, all-brick, built 1914. 7 huge garage bays in 2 separate wings of the building, a storefront that needs serious work, one finished 2-bedroom apartment, and 2 upper floors that are completely gutted and ready to build out. 6 electric meters in the photo, likely shared oil heat for the whole place, all new windows, new roof, new sprinklers, masonry looks OK from pics and street view. 

The problem is not having a foundation, septic, electricity or well to hook it up to.

@Allen Lopez Likely yes.You'll probably need multiple permits, because you'll probably be running electric into it (garage opener and lights).I would guess a construction and electrical at minimum.As other have said, get with the city, they'll let you know what you need

On the other floor, the current owner left an unfinished extra bathroom, walls to finish off in the laundry room, unfinished kitchen counters, a temp electric pole that needs to be updated to something permanent, and an ac unit that needs to be replaced.

The following week, they needed to shut the power to fix the siding behind the electric meters.

The building needs pretty much everything, including foundation repair, new roof, structural repair, new plumbing, heating, electrical, etc.