My wife is hell-bent on tile, but that is more costly and I'm concerned about maintenance and safety (especially in the bathrooms and kitchen...urine stained grout and cracked tiles where tenants drop their cast iron pan on the floor...eeek + slippery when wet!).

There are water stains and possible mold on the plank sheeting and some rafters in the attic area of the home that have been caused by leaking of the roof or leaking around the chimney flashing.3. here is active knob & tube wiring present in the attic area of the front home which is the reason for the ungrounded outlets present. 4. 

Cigarette smoke is what makes your walls and ceilings stain and smell because of the habitual lighting a cigarette.

If the drywall wasn't damaged to the point of crumbling and sagging, you're right just use a stain blocking primer and paint over.

I’m planning on doing a dark stain to help hide some blemishes, but the paint is a big issue.

Worst case scenario: Tenant didn't pay his utility bill and there are frozen pipes or a fridge full of spoiled food, some carpet is trashed, there are holes in walls and doors, and the place is full of pet hair, odor, and stains.

It is a different paint process and it can be very difficult to match paint or stain on pre-purchased cabinets. 

Generally this will not remove the stain.

They left the place dirty and in order to get the keys back I did not charge the usual such as cleaning, touch up paint, re staining of hardwood floors, etc.3 days after handing my tenant the deposit check, I receive a text message that he accidentally ripped the paper and check and needs a new one. 

Fans fans fans .. gravity will pull the water down fans will dry .. you may have stains as rust or dirt is pulled down through the drywall