Need advise on property purchase

I have planned to purchase a property and the deal is done & paid an advance amount & got the Agreement deed signed by the Owner. Here are my few clarifications still . 1) The owner is Rtd. Govt employee and he told me that he mortgaged property twice.1st is released and 2nd i should release it.The Sales deed & Linked documents are clear.The EC also reflects the same about the 2 mortgages. But he has not revealed to any of his neighbors that he is selling his property. Should i give a Public notice inviting claims before releasing property with 2nd pay as i am doubting something ? If yes should i take his consent before as he might drop the idea of selling it to me if i give a public notice without his consent ? 2) Who would deal with &bear the costs for any legal issue after the property is registered on my name ?Does the sale deed have provision for this clause? 3) Does owner have right to revoke agreement for any reason(in my case giving public notice) & sell to 3rd party?