Lister has it as single family, but it's a duplex?

[Megan Phillips]

My title search came back yesterday, and the town's lister has the property as a single family home, but the wastewater permit (circa 2013) for the property lists it as a duplex (also the MLS) and that's what I'm trying to purchase it as. According to the objection in the title report, it's the seller's responsibility to rectify this issue before close on the 30th. If not - it pretty much means I am not going to buy it.

If it cannot be changed, should I try and see about getting money from the seller to cover the inspection, appraisal, attorney title search, etc as it was listed as a duplex and marketed that way? 

I'm hoping it gets resolved easily enough, but who knows. I'm not sure how common this issue is or how it gets fixed.