A person who owns land can only sell it to others. Purchaser gets the same right which the seller has and if the seller has no right or has insecure right then the purchaser also gets no right or insecure right. Title Deed, Pattadar Pass Book, 1B register contains the details of the land owner. See all these three records to know whether the seller is the real owner. Encumbrance Certificate also shows the name(s) of the owner(s) and earlier transaction on this land