Taxes are relative. There are numerous Towns in Putnam and taxes will vary in each. However, Taxes take up a huge portion of your mortgage money so it is important to figure out what your housing budget is and then search based on that.
For instance: A $300k house in one neighborhood can easily work out to be as expensive as a $400 home in another. Why? The purchase price is spread out over 15-40 years. Taxes are every year.
With your desire to take the train, I'd want you to look along the Eastern and Western borders of Putnam. Stay out of the middle for the simple reason that it can be as long a drive to get to the train as it is to drive to the city.
Here is a cool Map Search feature that will enable you to search either all of Putnam County or specific locations.
MAP SEARCH
Here is info on Putnam County:
PUTNAM COUNTY (http://www.stlawrenceproperties.net/putnam-county-ny.php - broken link)