But also to identify lease violations before they mushroom into something worse.  

For example two mushrooms have grown in the bathroom there is a treehouse that is on poured footings that is falling apart.

(As for the gas, when they do the job, they just put the gas in the outside unit, put a newer inside unit in the house, connect them up, release the gas through the two systems and you're good to go again).8 years is nothing.AC companies live in a land where all the customers are mushrooms; keep them in the dark.

So just take a speed ball and enjoy the mushroom cloud. 

They could claim that told the landlord for several years about the mushrooms growing etc, and ask now US to refund unfairly collected rents.Is this a valid worry?

If HOA, the property may be in a super-priority lien jurisdiction where only a portion of the HOA lien has priority and the foreclosure of that lien does not extinguish any mortgages.A mortgage originated in 2006 would likely not mature until 2036... and if payments (principal, interest, taxes, insurance) had not been made for some time (especially on a neg-am loan), the current balance after escrow shortages and forced place insurance coverage could easily have mushroomed to $250k.Only the mortgagor (and the property itself) is responsible for satisfying the original mortgage debt... until a successor in interest acquires property subject to that mortgage, in which case it's still not the personal debt of the purchaser but simply attached to the property.Need more info here to be helpful.

When we acquired the building there were mushrooms and plants growing down from the ceiling that had roots planted on the roof.

Heck I bought a house that was growing mold mushrooms and it didnt cost 30k to strip it and redo it.