Agreement for gift deed

Iam a tenant on an unconstucted premises. I am to enter into an agreement with my landlords that states that they will transfer a part of ground floor of to be constructed multistoried building to me on ownership by way of gift deed. what is the validity of such agreement. would the landlords be bound by such agreement to execute the deed of gift. and if so what type of stamp paper be required for such agreement. Please guide me on this matter.