Requesting Tenant to Vacate Prior to Closing on Quadplex

Hello Family, 

I'm in the process of signing a purchase agreement on a quadplex.  The current owners are very generous and haven't increased the rent in 20 plus years for one tenant.  She only pays $300/month but refuses to sign another lease or give owners her phone number.  Anytime they need to communicate with her, they have to leave notes in her mailbox. In all honesty, I really don't want to deal with her.  If she vacates the unit, I can go ahead and start renovations.  I expect to receive $600-700 month/unit after renovations. Based on IN laws, since she pays month to month, I think they will have to give her a 30-days to vacate the unit.

In the purchase agreement, can I state Unit A, C, and D must be vacated prior to closing?  There is a tenant in unit B who has another 10 months on his lease.  He agreed to sign a new lease.  How would one write this request in the agreement?