I am a real estate attorney here in the Chicago area. Many, many REO Sellers try to pass on unpaid assessments for Condominium or Townhome Associations to the Buyers at closing. The funny thing about this to me is that almost all the contracts state that the Seller will bring assessments current to the date of closing. This is because the law that allows the Selling Bank to pass on the past 6 months of dues is an Illinois specific law, and the addendums to the typical real estate contract that the banks use are written on a national basis. I coach all of my REO buyers to be prepared at closing to make a stand and walk if the Seller tries to make these the obligation of the Buyer at closing, as it is a clear violation of the contract (realize this is in a situation where the contract states that the dues will be current as of closing). I have found that faced with that option, the Seller's attorney will go back to the bank, explain it to them, and generally we will end up closing a few days later. In this scenario, it is almost impossible to close on the same day, as this has to go through the hierarchy at the asset management office and the bank.
As a side note to other posters who will read this - Yes we have tried to work this out prior to closing, sometimes it works, and sometimes it does not. I have actually had Seller's attorney's offices certify in attorney review that all the back assessments will be paid by the Seller, only to show up and closing and have charges on the Buyer's side.