Buying a Property from a person undergoing divorce

Hi -- Can you please help me with this query? 1) Am looking to buy a property/flat from a man (seller) who is 50% owner of flat, with his sister owning the other 50%. 2) The seller's wife has separated and wants divorce -- she has not filed divorce papers in court, but has sent legal notice to the seller. The marriage lasted for about 19 years. They have two kids. The wife has alleged domestic violence (physical and mental) from the seller, her in-laws and the seller's sister, and the wife has also filed some FIRs in police station. 3) As per the wife's legal notice, the seller has five properties in Mumbai (including the property I want to buy). The wife has claimed (and wants) one property (other than the property I want to buy) as her matrimonial house, where she continues to live since marriage. The owners of this matrimonial property are her in-laws and the seller. Additionally, the wife wants some cash as well as monthly maintenance for herself and for her two kids. No other claims have been made by the wife. 4) The flat I want to buy was bought by the seller in 2010, and no one has lived in this flat since then -- it is vacant even today. 5) The wife's lawyer has sent a notice (not a court order) to the societies of all the five properties owned by the seller, telling the societies to not allow sale of the properties as divorce proceedings are ongoing. 6) In light of the above, I have the following questions in case I decide to make the purchase from the seller: (a) Based on the letter from the wife's lawyer, can the society legally refuse to issue a NOC to me for the flat I intend to purchase? (b) After I execute an agreement to sale (and pay stamp duty and registration charges), can the wife drag me to court in future and ask me to pay damages to her or prevent me from selling the property in future? (c) What safeguards can I put in place to completely protect me from the above situations? Thanks.