Gallatin county is the fastest growing county in Montana, and Bozeman is a great community.
Prices vary depending on needs, but there is a wide variety of properties available to suit any buyer. The market has been doing well compared to the rest of the country and is one of the best markets in the state. Montana in general has not been as affected by the recent changes in the market, and properties values continue to increase.
Bozeman itself is a growing city (in Montana a city is 40,000), and average home sales are around $210K.
For retirement purposes there are several communities around Bozeman to consider such as: Belgrade, Three Forks, or Livingston.
Depending on your lifestyle you could always look around Gallatin Gateway, Ennis, and of course Big Sky.
Land is ripe for development, and lots of builders are working constantly, especially in Big Sky.