Flushing crazy tenants from new duplex purchase

[Mark Hilgendorf]

I am buying a small duplex. I had Facebook messaged a girl I thought might be related to the seller, in an effort to reach the seller. She replied that she would let her know. Then I went through the real estate agent, made an offer ($28K, listed at $30K), had it accepted, and performed termite and sewer inspections. The seller told me that at close, the upstairs tenant would be leaving and the downstairs tenant would stay. We are planning to schedule a closing. After the inspections, I find out the single female upstairs tenant is the daughter of the seller, and she usually sleeps downstairs, with the single male tenant in the lower unit. It has been two weeks since the girl told me on Messenger that she would tell the seller I was interested. Last night I find out that the girl is the daughter, and lives in the building. She messaged me: "I am the upstairs tenant and the downstairs tenant is an amazing person and faithful renter. The terms you suggested are ignorant and you are going to lose both of us if you decide to buy. Which you won't because I'm making a bid." I was going to ask the man downstairs to sign a lease... now I am wondering if I should ask them both to move. I have not closed yet. If I need to, what is the best way to empty the building? Do I close and then evict? Or can I ask the seller to give them notice and to sell it to me empty. I am in Iowa. TIA!