Tenant with no lease situation urgent

[Imran Ahmed]

Dear Landlords,

So I am getting my first property, a duplex in Flagler County, FL closing at the end of this month where I want to occupy one of the units from July 1st. One side's lease ends in June and they wanna renew for another year with bumped up rent but the other side is on month to month. I don't want the m/m unit to stay as I want to occupy the unit. They currently don't have anything in wiring with the current owner that says they are on m/m just staying based on word of mouth as I was told they've been good tenants. When I met them yesterday the m/m unit told he can't move out upon sale which is May 31st (even though was notified when the property went under contract) and needs one more month. My worry is what if he can't find a place or might even not be willing to move out during the end of June when I will try to move in as well as planned? I'd be basically homeless during that time even owning a home and have to keep fighting with the tenant until he moves out and God knows how much hassle that's gonna be given this pandemic and all that. My question is how would you handle this situation and the safest bet?

1. Ask the seller to move the closing date a month out with addendum that the side I want to occupy has been vacant on closing?

2. Would it be possible to craft a legal document stating he has to move out at the end of June with no further extension offered as the new owner would occupy the unit upon sale and have it signed by him?

3. I just didn't wanna be in an eviction fight right after getting the property while I won't have a place for myself to stay either. Even the above signed doc might not help my living situation if they can't move out in time so is it even worth considering ?