Tearing up the slab and then repairing the inside of the house is the hard and costly part... especially if its already occupied.  

Are you buying this as a typical investment property or are you planning to househack/owner occupy it?

I occupy 50% of the building (~3,000 sq ft) with my Medical/Optometry Practice. 

It is currently fully occupied with month to month tenants.

With $20K, I would try to find something you occupy so you can take advantage of the low downpayment loans. 

@Adam Frantz before purchasing, if the unit is occupied, I ask for an estoppel to be completed if no hard copy of lease on file or lease is unclear and Addendum R plus proof of payment for the past 3-6mos.

Meanwhile, the relatively scarce individually-owned units are still priced relative to non-commercial RE market forces, including, among a variety of other factors, a lack of traditional financing options for the individual units (because of the predominant non-owner-occupied / single-corporate-owner circumstances within the complex). 

@Peter Halliday you said "residential buyer" but was it owner-occupied when originated? 

What are some of the best questions to ask a seller with a tenant occupied unit?

  $80k sounds pretty high to me even to tear-down-rebuild, which is probably an excessive approach just to make parts align right.The dividing line between owner-occupiers and investors in buying and selling decisions is the investor approach is the numbers.