Hello there,
The laws on rent differ from state to state, however, the only way to evacuate them is by paying them consideration for them to leave and handover possession peacefully, or contest eviction proceedings in the rent tribunal.
If they live for over 50 years, the law states that the landlord can either sell the property to him [preference should be given to him] since he lived there for 5 decades or let him continue living there. In order to vacate him in that place, compromise with him and pay him more than the advance amount for example if he has paid only 5000 rupees 50 years ago, advance pay him 1 lakh and ask him to vacate. It is very difficult to vacate him, even though the legal channel. These days no lard lord is interested in letting the tenant live there beyond 3 years and he looks out for new tenants fearing this problem.
Hope I could answer your query.
Regards,
Samayeta Bal.