How to know if tenant residing in my property(in Nasik,maharashtra) has bought flat / land /elsewhere?

Our old tenant’s son is paying measly rent of rs.20/month. I am sure he has bought some residence flat somewhere, as he is doing good business of selling “Vada-pau”. he owns a mobike and cell phone . such clever tenants lease out their flats and make a source of self income,, they continue staying in chawls paying low rents, always displaying a show that they are not well off & have no income.

How Long a Tenant should be kept?

does anyone have any idea in India how long one can keep the tenant. I was told after living in the same property some years the tenant can claim the property. is that true, if so, how many years is a safe period?
thanks for your response
I am aware of 11 months contract but how many years it is safe to keep the same tenant. I heard after some years, the tenant can claim the property, is that true?