Watch for knob & tube wiring (uninsurable), cedar post lally columns in the basement and slanted floors that result from the cedar posts shrinking over the decades.If they have been replaced, remember that the adjustable (temporary) steel columns are not up to code. 

Guns, Germs & Steel by Jared Diamond (not a business book but the scope of the book changed the way I looked at the world and improved by ability to process information), 3.

@Jonathan Greer a handyman to bore a 2” thick piece of steel 30 ft into the ground til it reaches a certain pressure?

My concerns are: -Some of the electrical isn't wired properly (double tapped)-furnaces 50+y old -various locations of water supply line show signs of leaks at some point-galvanized steel pipelines.

To do one space, I'm stuck with the awkward locations of the galvanized steel plumbing stacks, which limits flexibility of let's call them "modern layouts".

Also, couldn't find a curtain rod to span a window 12' wide so I had to make one out of steel conduit.

Steam radiators have bigger usually steel radiators but old hot water furnaces can also have a slightly smaller steel radiators. 

Quote from @Cole Steele: Hello, I am looking at buying a single family household to rent in or around Columbus.

Replaced all flooring, painted top to bottom, new fixtures, new stainless steel appliances, replaced counter tops, added back splash, repaired sheet rock on ceiling in laundry room, new front door and garage entry door to kitchen, new garage door.

Your getting 30-40% returns on these old steel mill houses .