Buying a property to live in do tenants have to move out upon closing?

I live in pa. my family and I are buying a multi family home which has 2 tenants. We plan to live in the home as well as my father in law. The tenants are month to month. How much notice do we have to give them to vacate the property? We can not afford to pay the rent on our apartment and the mortgage on the house for more than 2 or three months.