Firstly carry proper due diligence through a competent advocate and on confirmation regarding title etc only then enter into agreement. Payment be made in the name if owner only. In such case of POA holder sake various cases of fraud and cheating has been reported. So b3 extra cautious. 

you can proceed with transaction as sell has executed registered POA in favour of his son 

2)agreement for sale is binding upon seller legal heirs 

Yes you can buy the same it title is clear only do compliance of tds formalities 

- If the said POA is dully registered from the office of the sub-registrar , then the attorney can sell the property on behalf of the principal

- If that POA is registered , it means that the principal was present before the Sub-Registrar office for the execution of that POA 

- The sale deed executed by the POA holder on behalf of owner /seller is valid 

Check the apparent authenticity of the PoA by engaging a competent lawyer. Request him/her to check all the title documents and obtain a written opinion before going ahead. The PoA automatically lapses upon the death of the Principal. However, the agreement of sale made by the power agent when the Principal was still alive is enforceable against the legal heirs of the deceased.

Dear Client,

If the power of attorney (POA) has been duly registered at the office of the sub-registrar, it indicates that the principal personally appeared before the Sub-Registrar office to execute the POA. This registration process ensures the legality and validity of the POA.

With a registered POA in place, the attorney is authorized to act on behalf of the principal, including selling the property. The attorney, acting as the POA holder, has the legal authority to execute a sale deed on behalf of the owner/seller. This means that any sale deed executed by the attorney as the authorized representative of the principal is considered valid and legally binding. The registered POA provides the necessary documentation and evidence of the attorney's authority to carry out such transactions.

Therefore, when a POA is duly registered from the office of the sub-registrar, the attorney can proceed to sell the property on behalf of the principal in accordance with the law.

The POA deed will remain cancelled automatically upon the death of the principal.

You have to deduct the tax at source while paying the sale consideration amount to the seller at the rate as applicable to the NRI.

You better obtain a legal opinion from a local lawyer before venturing into the purchase.

You may proceed with the transaction by entering into agreement to sell with the seller through its authorized representative i.e. holder of General Power of Authority. The following precautions should be taken:

(1) It should be confirmed by way of an Affidavit of the POA that the owner (seller) i.e. the executant of the POA is alive on the date of the agreement to sell.

(2) The agreement to sell is properly drafted mentioning that the legal heirs of the seller shall be bound to this agreement to sell.

(3) Stamps duty on the full sale consideration be paid and the agreement to sell be registered before the Sub Registrar and the schedule for payment of the balance amount should be clearly mentioned in the ATS. with a clear schedule 

If the above precautions are taken then the seller as well as his legal heirs shall not be authorized to obstruct the completion of the transaction. Once the ATS is registered and the stamps duties are paid, the SALE is deemed to be complete subject to the payment of the remaining balance amount. You should pay the balance amount through the mode agreed in the ATS and have the receipts thereof in possession.