I would advise the complaining party that there is/was no evidence of smoking in the adjoining apartment she referenced and you have no choice but to consider the matter closed.

It consists of two buildings he has mortgaged and one building which is much larger that is owned by another party (it's a multimillion dollar downtown building that's out of my reach to purchase).

I have security cameras (mostly so I can prove if a guest violates the no-pets rule or throws a party, etc) and wifi door locks.  

that's been my experience with third parties 

It was a great deal for both parties, considering the buyer has 2 solid tenants with a 1% return MoM return.With the apperciation amount and inital capital, I set up a 1031 exchange.

I am looking to see if there is anything I can do from my (buyers) stand point to hold sellers accountable for this mess. 

@Tom Brickman ah, I think there are several pod cast episodes on this and other forum posts too and while it would take a lot to explain here I can at least sum it up.The BRRRR method stands for "Buy" "Rehab" "Rent" "Refinance" "Repeat".In the "Buy" step the investor targets properties that are in a challenge state from motivated buyers. 

In my opinion--I don't think they have a leg to stand on because the second dog was not legally an ESA (and probably still is not) when they applied for the unit given that the letter was expired.

In other words, they can't "launder" their title by washing it through a foreclosure and then redeeming and paying only the auction price.If the bank still owned the property, and there was a balance due on the note for after the foreclosure, the redeeming party would redeem from the bank and have to pay the full balance on the note, not just the auction bid price. 

Management of vacancy and maintenance are the two largest costs of 3rd party management.