Promoter not giving lease agreement

Dear sir, with due to respect i israr ahmed from kolkata west bengal my brother is purchsed a property in cooperative housing socity in kolkata we clear all payment and ocupythe position when ever book the flat promter a sold the flat lease agreement for 999 year and taken high amount per sq ft now this time they are saying lease agreement is not possible so you are giving rent and stay tenancy basis so i want to know how to handle this situation we havent any agreement paper for flat booking because promoter is in my realation we have only psyment recipt in normaly mony recipt normal paper a