Tenant for last 20 years landlord died his son sold property

Dear Sir, I have been living in an asbetos shed house build by us at our own cost on a terrace for past 20 years. I have paid around 30000 in advance to the land lord at the starting and a rent of Rs 100 was finalized. But no lease/agreement was made as landlord was a very close to our family. I paid the rent for the first month and thereafter no payment was done as he didn't came to collect so. But now he is dead and his son has sold the plot to some promoter who is about to build a 5 storeyed building and asking us to evict saying we are being illegaly there. So what rights i do have ,