Documents to verified

Dear sir,

I am buying a shop in a shopping mall in mumbai,

i would like to know!!!what are the documents that needs to be checked,???hence i am buying it from the second party???and the mall is still in the possession of the builders!!recently it has opnened!!

but the thing is that,,,the shop which i am purchasing from the seller has been bought by the seller a year back!!!!

in that case what are the documents that needs to be checked compulsory and how the deal should be executed!!!!

hence there is a agent in the middle,and the party is the registered in that brokerage firm 4 or 5 months back!!!