Paint

Today I had a issue with a tenant in one of my rooming homes that makes me think maybe I should put EVERYTHING in writing.  Somethings seem self explanatory or common sense, but when dealing with people I think that assumption is to be determined.  I go to the house to put in the household necessities and the door to one of the rooms on the lower level is open so I glanced in and noticed the walls have been painted. Now I wouldn't have an issue with this if the tenant asked and if it was an appropriate color (neon yellow). I am upset and don't know how to handle this because for starters its not in writing, once you let one person get away with it then its like a chain reaction, dont want to lose a tenant / income, and when they leave I have to paint it back.

Smoking or Non-smoking?

I usually don't care about the smoking in my homes, but lately I have noticed that more of my tenants smoke.  This isn't really a problem but I have been having to paint more than usual. Ive also noticed that it has caused the mirrors in the home to stain or become cloudy due to smoke and the poor maintenance. The homes have a odor and appears to be dusty.  There are a few tenants who don't smoke and have put complaints in the complaint box, but I'm not sure of what I should do. In a since I think it would save me some money on paint and cleaning products but having non smokers may cause me to loss tenants. Indecisive on what I should do.