Condo Dumping

Does anyone have any impressions if condo owners in a building are in a frenzy to sell? I know of a building where several units have been sold in the last few months. The owners say nothing other than they have other plans. How do you get a seller or the seller's broker to be forthcoming with as much informationa s possible prior to signing a contract. For example, is there a pending assessment, known issues with the building, violations from teh city, pending lawsuits against the condo board, etc. How do you make sure these are all in the contract prior to signing> If something is missed an information is withheld, what can a buyer do once in contract?