Ownership, Mortgages, Violations and Deeds:
A number of New York City agencies make certain building information available online. On some sites, you can can look up the information by building address, but for others you will need the borough, block and lot number (click here to find a BBL).

The Department of Housing Preservation & Development (HPD) has recently made available Building Code Violations and other information through HPD Online. Here you can look up the BBL if you only have the address, find out the registration of the building, census tract, stories, units, and emergency repairs. When you go to the HPD online page, scroll to the bottom and click on the link to PROCEED TO HPDOnline >>
click here to visit HPD Online

The Department of Finance has created Automated City Register Information System (ACRIS) that allows users to look up property records and transactions on specific properties searching by block and lot number, or do research on a particular party name. Mortgage and deed transactions are posted, and many include scanned images of the actual documents.
click here to visit ACRIS

The New York City Open Accessible Space Information System Cooperative (OASIS NYC) website allows users to look up property information and block and lot maps, searching by address or block and lot. You can find out lot size, zoning information, ownership info, and links to other property information. The site continues to improve and is a great place to start looking up information on a property.
click here to visit OASIS NYC

The Department of Buildings (DOB) offers real-time Building Information System (BIS) data including a property profile overview containing detailed complaint information. It includes DOB violations as well as Environmental Control Board (ECB) violations. You can also sometimes view the C of O for a property, or any permits issued.
click here to visit DOB BIS

The New York State Department of State maintains a database of corporations registered throughout New York. If the owner of a building is a corporation with no name or address, you can look them up and see who the real owners are.
click here to look up corporations at NYS DoS

The Department of Finance has made J-51 (tax abatement) information available online. You can check whether or not a property has received any J-51 benefits over the past 30 years by searching by borough block and lot.
click here to look up J-51 benefits at DOF

Property Tax and Water & Sewer Information:
The Department of Finance allows users to look up both property tax information and water & sewer information online. You can look up property tax information on any building on two different sites. The epayment center allows the user to make payments and the property reports site allows the user to check the assessment roles. Water & Sewer billing and account information is also available online, but only by account number. This means you have to already know the account number to look up the information. You will be able to make payments and check payment history through the epayment center. You'll need to create a username and password to access the more detailed records on the property reports site.

click here to find property tax and water billing data through NYC's epayment center

click here to find property tax and water billing data through NYC's property reports center

Other Data:
The NYCHANIS (New York City Housing and Neighborhood Information System) site is up and running, created by the Center for Real Estate and Urban Policy at NYU Law School. It lets users access data from the Housing and Vacancy Survey, Census and a number of other sources, by census tract, community district, sub-borough area, zip code and political districts, and even has mapping capabilities. You'll need to create a username and password to use this amazing site.

click here to access NYCHANIS

The NYC Rent Guidelines Board's housingnyc.com, has a host of nyc housing data, including their own studies on mortgages, income and expense, and their rents, markets and trends reports. It's also a good place to go to find about tenants' rights and rent guidelines, They also have Housing and Vacancy Survey data, but only at the citywide level.

click here to download reports by the rent guidelines board

The InfoShare website provides access to an abundance of data -including housing data and information (including demographics, public housing and nonprofit organizations) - at many levels, including NYC Neighborhood, Community District, Census Tract and by political boundaries. This site is highly recommended and easy to use, but you do have to register.

click here to visit the infoshare website

If you are looking for nonprofits that provide services in the area of housing and shelter, the New York City Service Atlas is a great site to use. The site will let you search by zip code, city council district, neighborhood or community board, and provides decent maps, thanks to nypirg's cmap program.

click here to access the New York City Service Atlas

Demographics
If you are looking for demographic data related to housing, you will probably find it under demographics.

click here to look at housing data under demographics