Recommendation for an expediter in NYC - Brooklyn

[Song Ceng]

Hi. I found a buyer for my house in Brooklyn. I brought my house as a 2 family (2 gas meters, 2 electricity meters, and been paying tax for 2 family since brought in 2003). The buyer's title company found a CO from 1924 showing the house as 1 family. But I've since found paper from DOF showing the house was registered as 2 family as far back as 1937. Is there an expediter that you would recommend to help with submitting request for letter of no objection? Or is it better off if I submit request myself?