Below are some links put together to hopefully assist you.
NYC Department of Finance:http://www.nyc.gov/html/dof/html/home/home.shtml
On line NYC Register: http://a836-acris.nyc.gov/Scripts/Coverpage.dll/index
NYC Rent Guidelines Board: http://www.housingnyc.com/
NYS Division of Housing and Community Renewal: http://www.dhcr.state.ny.us/
Rent Stabilization Association: http://www.rsanyc.org/
Real Estate Board of New York: http://www.rebny.com/
NYC Dept. of Buildings: http://www.nyc.gov/html/dob/html/home/home.shtml
NYC Dept. of Housing Preservation & Development: http://www.nyc.gov/html/hpd/html/home/home.shtml
Landmarks Preservation Commission: http://www.nyc.gov/html/hpd/html/home/home.shtml
The New York Landmarks Conservacy: http://www.nylandmarks.org/
NYC Real Property Income & Expense Forms: http://www.nyc.gov/html/dof/html/pub/pub_property_rpie.shtml
Click on the category you are interested in: