What constitutes separate apartments?

[Pearson Caldwell]

I am in the process of buying a home. The home is currently zoned as a two-family, but it has three stories with three separate apartments. The second and third floor share utilities, with the second floor covering utilities for the third floor, and the tenants agreeing upon the set temperatures, etc.

The appraisal came back and said the appraised amount is contingent upon "proof that the third floor has all proper permits (building, electrical, and plumbing)."

My lender interpreted this to mean that the home must be zoned as a three-family, and they will not underwrite the loan for a three-family home without 20% as a down payment (which I cannot do).

I don't know that the interpretation of "proper permits" is entirely correct. Per my city's laws, four unmarried adults may share a residence, and there are only three tenants between the two floors. Given that they currently share utilities, could I argue that the two sets of tenants are renting out individual floors of one apartment?

If the apartment must be rezoned, I will have to get a new lender, new appraisal, extension on the mortgage commitment and closing date, and wait for the seller to rezone. I would obviously rather avoid all of that.