To re-mediate issue, I hired a handyman and re caulked the shower.

These were violations I did not know about...apparently no fires within 60 feet of any building so I am now taking these steps to remedy the situation.

We've have had similar problems with both pets and garbage (apparently the garbage bin, at the side of the building,  is "too far" of a walk, so they leave bags on the fire escape for the raccoons and crows to rip open and shower down on the neighbourhood).We first sent a letter to all tenants reminding them of their obligations for their pets, pets belonging to their guests, and their garbage.When that didn't work, we sent another letter proclaiming our disappointment and the actions we were going to take to remedy the situation ... namely hire someone to pick-up the dog faeces and garbage and to ensure the garbage is put curb-side for pickup on garbage day each week.  

Sometimes cash for keys is the best remedy with unruly and disrespectful tenants.

The recommendation is for remediation of all three rooms. 

Be careful who you bring in to complete remediation if you find anything. 

When we remediate lead paint we never have to touch the walls.

Of course, there is mold everywhere, so no such thing as negative, but I have an air test done & the results come back extremely low - lower than the average outside levels for that region.I tell him good news, safe levels, he says I'm getting sick and it doesn't matter what the test says, I want it remediated ($3k job). 

The water heaters are way past their lifetime so I would probably address them first because they cost a lot less to remedy as compared to the furnaces.

Still in due diligence and have alerted buyers agent that we will be going back to seller with a discount on the offer to take into account the odor remediation.