You can call your local building department (DOB) in Brooklyn. They can give you the info you will need also the best route would be to call 311 and they can give you the direct number to legitimate companies that do this. One of my neighbors did this, here on Staten Island, and they knocked down their large home and built 4 in it’s place, but they still haven’t sold and it’s been 2 years…long story…anyway they did what your trying to do. I say remodel that brownstone. It will pay off 10 fold! Also check out my website to give you some ideas of what you could do at

Hope that helps you!