Licensed with permits ~$3,250.HWT standard gas single family low efficiency without exhaust retrofit $900.Sand and stain hardwood floors, natural stain $3 per sf.Paint interior walls, ceiling trim and doors 3 tone paint scheme 2 coats $3.20 per sf (floor area cost includes paint)Click lock LVT flooring install overlay inclusive of prep and quarter round $4.50 per sf (materials and labor)Asphalt roof installation 3/1 - 800 sf bungalow with 2 layers of shingles - ~$7,900Standard porch cap replacement with 2 new precast concrete steps ~$2,500Used stove or refrigerator delivery and install $350New stove or refrigerator delivery and install $HD model specificUse this as a general guideline. 

However the thermostat is mounted  to the wall a few feet from the front door in a highly accessed retail store where the door is constantly opened.

Water is now leaking through the ceiling into my tenant's unit, and it's worsening with every rain also the neighboring unit has sever water damage (like a pool inside and it is owned by the HoA) and water from it leaking very dirty water from the shared wall to mine.

Quote from @Jaron Walling: I bought my first house and got into REI for control, stability, and the opportunity to solve problems. 

I'd personally say pulling your water heater out and replacing with a wall mount on demand one, would be worth the cost to have in unit washer dryer if you are staying there or renting it, it would be worth it.its always worth doing the big stuff well and correct even if you are cleaning up after someone, the long term hold always prevails, its just a little frustrating front sometimes, but hang in there!

My current tenant has removed a picture from the wall and replaced the provided bedding with their own belongings. 

Helps with your debt to income, better opportunities at cash flow, and typically requires less down to purchase.In regards to challenges, I usually build in an extra 10-15% to deal with things that I can't see behind the walls, including dry rot, electrical or plumbing issues, etc.

Evan took an online class and learned how to replaster walls and yes I do mean old school plaster.

For example, the 2nd to last photo of a random wall and floor with part of open door; what is that supposed to be telling?

The units all have tri-paint jobs with ceiling paint, a nice wall color and super-white glossy trim on everything else.