You will be hard pressed to find one single agent that can help you in both places. The vast majority of successful agents find one specific area which they know and know how to sell. Real estate is a very localized industry. Especially when you compare Brooklyn and Staten Island. This is because there are two completely different Multiple Listing Services in Brooklyn and Staten Island. In Brooklyn you have the Brooklyn New York Multiple Listing Service (BNYMLS) and in Staten Island you have the Staten Island Board of Realtors (SIBOR).
You would be better off having two agents help you, one in Brooklyn and the other in Staten Island. If they happen to be affiliated great but that is not mandatory. The important thing is that which ever agents helps you, they should a) be experienced, b) be trustworthy and c) be an expert in the exact area in which you are looking to buy or sell.
If I can be of further assistance please let me know. I myself specialize in Brooklyn, but I do know some great agents in Staten Island which I can refer you to. If you have a property in Brooklyn you wish to sell, I would love to hear more about it, I may have a buyer for you! Good luck!
Mitchell S. Feldman
Associate Broker/ Director of Sales
Madison Estates & Properties, Inc.
Office: (718) 645-1665/ Cell: (917) 805-0783