Only contracted out the cement, Sheetrock, well, and asphalt driveway.

Would the fridge’s journey involve stairs or any other obstacles or is it right next door?

From cement, studs, flooring, etc.

I would stick with carpet on upper floors in bedrooms and on stairs.

If none of those solutions will work, and they are MTM, you can give them notice and terminate their tenancy, repair the stairs and re-rent out the unit. 

To allow that money to go to waste would be a shame and would likely cement in stone that I would not go any further than reading or posting.To summarize this post, challenges can either be your motivation or your demise.

Under stair storage is a bonus.

If I rent the rooms MTR, I'd still be short $1600/mo (0.85%).The property has a cottage, split into a micro studio and a one bedroom, and a 3/2 house with a semi-finished, stair-accessible, windowed, empty attic 75% the size of the house. 

This includes repairing the front walkways / stairs and deck areas. 2nd phase will start in the Fall and be completed by EOY.- The last SA took place 3 yrs ago for a new elevator which is currently part of the building.

Quote from @David Perry: Liability insurance covers accidental property damage by your tenant (e.g. kitchen fire) or personal injury (e.g. fall down the stairs).Talk to your insurance carrier and ask them for advice.