Closing tomorrow and found out there's a tenant 24 days late

[Jeremiah H.]

I've never had this situation arise before and I'm looking for advice. We are closing tomorrow on a duplex that is currently rented out. One side has a tenant that is month to month and below market value. We were going to approach this tenant immediately to sign a yearly contract for market rent or ask them to move out in X number of days, being completely reasonable about the timing. 

The second tenant is 3 months into a year lease and hasn't paid for this month, which was due 9/1. The seller is suppose to pay the prorated rent amount until the end of the month and when they sent over the HUD they said they were going to pay this amount "even though they haven't collected rent this month yet". This was how we found out about the late tenant, not a call from the realtor. I'm not sure if this is common with multifamily properties, but these are nice units in a good neighborhood. It would be abnormal to have a bad tenant in one of these properties and I feel like it's something that should have been brought to our attention much earlier than 24 hours before closing.

What should I do, both before now and the closing and immediately afterwards? I don't want to take over a unit with a tenant that will likely turn into an immediate eviction (which I've never done before).