If it is walking too loud I have told tenants to work it out between them but I have had to tell tenants no powertool/workshops,  Super loud music, incessant barking, clogs/drunken shenanigans on the stairs  and kids running the hallway after quiet hours. 

WE took down a 15x20 shed on cement block piers with steel I-beams across them.It surprised us that there was no cement between the blocks but 1" square steel posts inside each pier.The 'shed'  even had oak hardwood floors like those inside the1949 era home so we assume it was built then.. 

And fake cement board that looks like asbestos siding for patch work is not cheap either.

@JT Spangler  - 230k in Santa Cruz gets you the cupboard under the stairs and bathroom priviledges on nights and weekends.

home needs paint, here is a list that I got quoted $7,500.00 for Ive bought wall paint alreadyHe is supplying everything else, tape, brushes, trim paint ETC.Paint entire 3150 Sq ft home Paint ceilings Repair texture and paint water damage in 3 areas of the ceiling Paint entire 2 car garage Paint all oak cabinets White, sand, prime and paint correctly off hinges probably 25 doors, and 15 drawers Paint all 12 doors paint stair case wood polespaint baseboards the foyer has very high vaulted ceilings. it is a decently large home as well. 

Leave the carpet on the stairs?

No cement.

Maybe soften the square-ness (if possible without adding major work) by angling the corners and add a stair all the way around.  

It was frozen to the cement so I couldn't lift it to look underneath...

I even had a broken cement double laundry sink that leaked.