NYC HIC Registration

I live and do most of my work i NJ, where I am insured and registered, however, my brother lives in NYC and is starting to ask questions of me that I can't answer. He owns his own company and he wants me to trim out an office for him and built a reception desk...in NYC. Also being he is in the real estate business, he sometimes can get me leads on work to be done...I looked into the NYC pages and really didn't find much in the way of out of state contractors. I want to do this legally...can someone point me in the right direction, if not I will have to go find someone to talk to in person, but any info would help. Thanks.