Westlaw has a database for real estate news articles (RPNEWS). Lexis has a file of articles from real estate trade journals (REALTY;PUBS), including Shopping Center World (NEWS;SHOPCW).
The Jack Brouse Real Estate Library at New York University's Real Estate Institute has an excellent collection of resources in very practical areas such as: shopping centers, hotels, coops & condos, REITS, among others. They are open to the public, a terrific resource if you can get there. Check out their Research Guides and/or search their Catalog to identify useful materials.
The Real Estate Research Institute posts abstracts of real estate-related research papers on the Internet. You can buy the full articles from the Institute.
Land Records: Many states, cities and counties now post images of deeds, mortgages and other land records online. If you can't find a government site, or if you need more information, try Zillow, which is free. Fee-based land records services include Data Tree's DocEdge service and/or Lexis. If you just need deeds, Westlaw has a deed image database (DEEDIMAGES). Otherwise, you will probably have to send someone to the local Recorder of Deeds office to get copies of land records.
The National Conservation Easements is compiled by a nonprofit organization called the U.S. Endowment for Forestry & Communities, Inc. The database is not comprehensive, but is potentially useful for searching.
For additional information about a property, check the relevant tax assessor's database (usually either state-wide or for the particular county).
See also "Title Searches," below.
Foreclosure: Many states post information on foreclosure actions, either in separate databases or in their regular docket databases (see "Docket Sheets" and "Liens"). Westlaw offers a selection of "pre-foreclosure databases" with records of lis pendens notices, default notices and notices of sheriff's sales (RPF-ALL to search all the available states; RPF-xx for an individual state).
Landlord-Tenant: Landlord-Tenant law is generally governed by state law. The leading treatise in the field is Friedman on Leases (PLI), but there are also many state specific treatises (e.g., Maryland Landlord-Tenant Law). You can find state-specific L&T treatises by by looking in Searching the Law: The States by Francis R. Doyle (last published in 2003) or by searching the online catalog of a law school or government law library in that state.
To determine whether a landlord has a duty to mitigate the damages in the case where the tenant defaults, see Appendix 16A of Friedman on Leases and/or the article, "Landlord's duty, on tenant's failure to occupy, or abandonment of, premises, to mitigate damages by accepting or procuring another tenant" (75 A.L.R.5th 1).
Note: The "Tanbook" is the nickname for a desk book officially title, New York Landlord-Tenant Law (LexisNexis).
Leases, Commercial: For a review of the relevant law in each state, see the State-by-State Guide to Commercial Real Estate Leases (Aspen Publishers). Insider's Best Commercial Lease Clauses (Vendome Group) is good for forms. The Commercial Lease Law Insider (now by the Vendome Group, formerly Brownstone Publishers) is a good periodical for current awareness. Aspen and Vendome both have additional publications on the topic.
Pollution: You can identify all the pollution sources in a city, county or zip code in the U.S. using the EPA's Envirofacts Quick Start! search.
REITs: The National Association of Real Estate Investment Trusts (NAREIT) posts lots of REIT-related information, especially in the "Documents on Demand" section. The site also has a bibliographic database called RealSource that lets you search for journal articles related to all aspects of real estate, but you have to get a password (which takes 24-hours and I think costs money if you go beyond the 30-day trial period). Standard & Poor's rates stock and debt issued by REITs. Subscribers can get deep data on REITs from the CRSP/Ziman Real Estate Database.
Sale Prices: Many states and municipalities provide free searches to find records of real property sales, including sale prices; BRP Publications posts annotated links to many of these Web sites (choose the state and then find the "Real Estate" links). For private homes, you can also use Zillow. In addition, all the fee-based databases discussed in the "Title Searches" section, below, also provide sale prices.
On the city-wide or national level, the leading measure of U.S. home prices is Standard & Poor's Case-Shiller home price index. Data is posted back to 1987. Figures are also available from the Office of Federal Housing Oversight (OFHEO), which covers homes financed by Fannie Mae and Freddie Mac, and the National Association of Realtors (NAR), which reports the aggregate price of homes sold (rather than whether the price of an individual home would go up or down).
Title Searches: You can generally find out who owns a parcel of property by using one of the several public records databases offering real estate ownership & sales records. Many states and municipalities post free databases online (see, e.g., the "Property" links on SearchSystems.net or BRP Publications). Otherwise, leading fee-based vendors include Accurint, Lexis and KnowX.com. These vendors also have databases with lien, mortgage and foreclosure information.
For more sophisticated results, you can try pulling a History and Vesting Report from DocEdge.
For the most current and reliable information, however, send a professional title searcher to the relevant Recorder-of-Deeds' office for a comprehensive search.
Valuation: The materials used by appraisers to accurately value real estate are published by Marshall & Swift. For a quick estimate of a property's value many people use Zillow, but I recommend focusing on the "comparable sales" and, if possible, visiting the homes. If you look up the last sale price for a residential property (see "Sale Prices," above), the Federal Housing Finance Agency's Home Price Index Calculator will figure the current price based on average property values.