Rental rates vary depending upon the type of commercial property you are looking at (is it office space, an industrial complex, retail, shopping center, etc.) as well as the location. An excellent site to find and compare data on commercial properties is LoopNet (http://www.loopnet.com). When you go to the site, you do a search which is "commercial real estate for lease" and then you select specific criteria regarding the properties, and narrow it down to compare to your properties characteristics . You should enter the zip code, which for Fort Greene is 11205. You can also select from the rental rates from the drop-down menus, and click on properties similar to the one you seek. Further breakdowns are possible by selecting the rent per month or per year. You can refine your search by any criteria you select.
It is probably best to consult with a real estate agent who specializes in commercial properties.
Bonnie Chernin & David Rogoff