Purchase of flat from nri

Hi,I have a query:

I want to purchase a flat from an NRI from USA. He wants to sell the flat through a power of attorney. As a purchaser do i have to take any prior approval from RBI or any other permission under the FEMA Act 1999 for this purpose? This transaction is covered under which rule of RBI? Should i take perission before remmitting any money to an NRI by way of purchase consideration? Please help me