Maybe you should telephone a Realtor and ask what's for sale. That way you can be more specific and get a straight answer--which of course I couldn't give you with the very broad question you have asked.
Your question struck a chord with me so I thought you might be interested in my blog post that answered a similar question that a received a while ago.
You can click on this link http://db.tt/7KwnmlYv or paste it into your browser to see the blogpost.
As far as Londonderry is concerned if you are dealing with residential property, then it would be helpful to know what the minimum lot size in town is (of course there will be smaller "grandfathered" lots).
Contact Arlene Hajjar at RE/MAX 1st Choice for additional assistance in town. 603/490-1001, firstname.lastname@example.org.
Chuck Braxton, REALTOR GRI