Subscriptions in websites is a very common requirement. This is not a module as such but the best solution for this I have found is to use Ubercart attributes with which I have set up at least half a dozen sites.
A listing search system based on geographic location, proximity and category. These listings initially cover North America but eventually will cover the globe. Users enter either a city / state combination or a zipcode, select a distance and a category (optional). The resulting listings have addresses that lie within the selected distance from the selected location that belong to the selected category.
