I would just excavate a few 2'x2'x2' (or larger if possible) spot footings, w rebar and Simpson hardware,under the house (you will want to take up the floor to make this easier to do).

Renting out a room is a great way to get started, and I wouldn't get too settled into the "going rate" use that almost as a floor. 

With foundation issues, one could have plumbing, drywall, flooring and even roof issues and alot more.

Keep the wood (or sheetrock if you choose) an inch or two off the floor to not wick water.

So many of the builds I've visited, some multiple times, seem to be frozen in time: the homes are dried-in (roof paper, windows and doors), tiled floors, drywall installed, and then a dead-stop.

Great to meet you.We source from four primary suppliers: Lowe's, Home Depot, Floor & Decor, and Amazon.

That led to uncovering significant water damage throughout the first-floor unit's bathroom, forcing an immediate renovation.

Quote from @Ricardo Polanco: Good evening everyone, I am evaluating the possibility of buying a multifamily property in Scranton, at this moment it has 2 apartments that only need cosmetic repairs and it has a big 2nd floor unit that needs a full repair.

The 6.8 was some 65 miles south of me, I was on the 2nd floor of an office building that shook so hard for a minute that people were having problems staying standing up.

I think you are looking at the wrong places, insulating the floor wouldn't change much.