Told I was buying a legal 4 flat, zoning came back as a 2 unit

[Benjamin Sussman]

I made an offer on what was advertised as a legal 4 flat. The sellers lawyer provided zoning documents which state that the building is only approved as a 2-unit building. 

To make matters more confusing, my county's assessors office, Cook County, stated that the building was a 4 unit. The seller is offering me a $2,500 credit on the home due to these zoning issues. The language used by the sellers lawyer regarding these zoning issues can be found below. 

Any thoughts on what I should do? The property has great cash flow as a 4 unit but the place wouldn't even breakeven as a 2 unit.

While Cook County Assessors Office website indicated that the Property has 4
Apartments (including Full basement and Attic), when zoning was ordered, zoning
compliance came back as a two (2) Unit. Please see copy of Assessors Website page
relative to the Property (printed on 10.9.2020) and recent zoning certificate. In an
effort of good faith, Sellers are willing to offer a credit of $2500.00 in order to pay
for any corrected zoning, which may or may not include: Architectural
plans/drawings; engineering requirements and any costs for re-zoning.

[Brie Schmidt]

@Benjamin Sussman - the assessor is never right and shouldn't be considered a reliable source.  $2500 is nowhere close to adequate.  PM me the address and I will dig a bit