@Katherine Serrell Thank you so much for your input! I completely forgot to include my state. The property is located in Bucks county, Pennsylvania, specifically Levittown.
I have reached out to a recommended real estate attorney and am waiting for him to get back to me. I was thinking the same thing about applying for the zone exemption, but I heard it is very difficult for the township to grant it in this area. There does not appear to be many duplexes and they actually have stopped allowing duplexes to being built for 15 years now. I was just wondering as to who would be at fault before this goes any further. I feel really bad for my client and want to do everything I can to ensure he's taken care of.
That's a good point about the insurance company. I will have to reach out and have my client double-check that. The mortgage lender was also under the impression it is a duplex, so the mortgage is structured for a multi-family property brining in income. Thanks again for the information! I'm hoping it works out for the best.