Not sure what State you are in but a list of things to fix within 48 hours of a move in is common in my neck of the woods.

I like to do LVP on the stairs too, with white wood risers and the LVP "bull-nose" tips.

I wouldn't recommend wasting your time with filling with any product if the wood is soft and rotted.

Anything porous like carpets, drywall, insulation, wood laminate flooring, etc should be tossed and replaced.

The FHA Appraisal also has pretty specific sections including: No damage to the foundation, roof, or exterior, Safe access to the premises, Working utilities, No exposed wiring or other electrical systems, A permanent heating system that provides sufficient heat for the home, No peeling or chipping lead-based paint, Access to clean water, No termites or other wood-destroying insects, Access to, and ventilation in, attics and crawlspace, No soil contaminants, such as from a damaged underground storage container, No safety hazards, such as stairs without handrails, Compliance with local zoning regulations.

What to do:  The 14 day time frame is unrealistic to a situation and I'm seeking input on what to do:Tenant left cat urine soaked wood flooring. 

Furnace and AC filters, dryer vent cleaning, gutter cleaning, smoke detector batteries, storm drains, wood burning fireplaces/chimneys, exterior window washing, roof cleaning, you name it.

With the barn, see if someone is willing to pay you to take it down and take the wood. 

That price is about right for a cable railing, depending on species of wood for the posts.

Purchase price: $4,000 Cash invested: $15,000 Tiny home on wheels that has been placed on 25 acres of woods with trails.