Is green card enough to show multifamily status ?

[David Smith]

Green card clearly says it is 4 unit. And the building has four meters for sewer, water and electricity. 

In NJ , the state , not city , regulate and inspect the multifamily. 

During closing, both buyer and seller attorneys agree that greencard is enough for proof  its multifamily status and ready for closing.   The problem is the lender attorney is asking a document from city to say it is a legal 4 family from seller.  It is crazy ?  

what to do ?  Also it is buyer duty to prove and investigate.