Regardless, the lender and title company should have discussed any amount due prior to closing when your offer was accepted. 

You are correct on doing due diligence on prior liens.

About an hour prior to closing I showed up to do my pre-closing walk through to verify the house had not burned down and to retrieve my lock box.

It all depends on when their prior lease ended and what the clause said regarding the lease automatically renewing. 

Current or prior ownership of real estate: Currently own 1 rental house in Portage,IN and have only my DP in equity, 25% but comps in the area show property worth another 10K (+ the 25K down)Occupancy: 2 homes pay land lease, 4 long term renters and 5 other homes leased with an avg 90% occupancy.Value of property at present and/or your offer price: $175K list and seller is willing to leave 12K in escrow return to buyer after purchase.

Current or prior ownership of real estate: Currently own 1 rental house in Portage,IN and have only my DP in equity, 25% but comps in the area show property worth another 10K (+ the 25K down)Occupancy: 2 homes pay land lease, 4 long term renters and 5 other homes leased with an avg 90% occupancy.Value of property at present and/or your offer price: $175K list and seller is willing to leave 12K in escrow return to buyer after purchase.

 You should review your state's rental property laws or consult an attorney.Usually the state requires a certified letter of lease non-renewal to be sent to the tenant's residence 30, 60 or 90 days prior to the ending of their lease. 

I've used that calculator I just didn't know if it would give me accurate numbers based on me living in it prior.

@Timothy BorgIf you are going to do a refi you will need the prior seller to provide an authorization to order payoff for most lenders, or at lease provide a social security number, depending on lender.

You need to find all the issues with the property prior to the due diligence expiration use them as bargaining chips.