Not sure if I mentioned looking for maps of the area you wish to model, but if not, here are some ideas:
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Sanborn maps - first made by the Sanborn Company for fire insurance purposes, it lists buildings as well as railroad rights-of-way.
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Topographical maps - can be found online, and will show track locations (usually older locations, depending on when the maps were made). Also shows abandoned tracks, if one is interested in the location of whatever bygone railroad was there.
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Online satellite images - Yahoo and Bing have these features, but my favorite is Bing. You get satellite images of almost every place on the globe. Caution: some areas may not have sharp pictures when seen up-close. Bing has a birds'-eye view which allows for sharper, closer pictures. This is a feature better used for latter-day modeling, since almost invariably track arrangements change (and in some cases, vanish altogether) over the years.
Please note that the above suggestions are most helpful for prototype modelers; however, if you're interested in freelancing, they can work just as well.
