ABOUT FORECLOSURE LISTS:
Because a house is listed on a foreclosure site does not mean that it is for sale. A homeowner must have intent to sell or it is not available to be shown. A property shows up on an internet list on a foreclosure site because a company has compiled public record filings of legal notices; not because a seller is representing he/she wants to sell a property. The first step is to determine if the homeowners of the properties you mention want to sell. They may, or may not, want to sell. If not, any approach from you may be regarded as an unwelcome intrusion.
There are reasons other than mortgage default that can cause a property to go into foreclosure, but falling behind in mortgage payments is a common reason. A mortgage company will file papers to place a public notice that the company has started a foreclosure process. There are several companies that collect the public filing notices from counties all across the country. The list that they publish is a compilation of properties that are the subject of public legal notices.
When sites list foreclosure lists under "property for sale" and they are not for sale, it causes confusion for the public, and compromises the integrity of the site. Until a homeowner sues a site for damages (intrustions, etc.) that the misresprentation caused, it will probably continue.
Property owners can fall behind in their payments and find resolutions through a variety of options. A Realtor may be able to assist you in determining if these property owners have an interest in selling. A strong buyers agent will approach homeowners who are not actively selling and inquire about the possiblity of selling. Buyers agents do this all the time, and it has nothing to do with whether a property is in foreclsoure or not.
ABOUT BUYING FORECLOSURES:
Properties in foreclosure can have many liens beyond the mortgage, and clearing these liens can be quite expensive. If several liens to be cleared to pass title, the acquisition cost for these properties can supercede others on the market. While "foreclosure" may be a big buzz word, the fact is not all foreclosures are for sale, and of those that are for sale, many are not "good deals." Don't let misconceptions lead you down the wrong path.
A Realtor will be able to help you sort out the information.