I would suggest reading Google's Terms of Service
, particularly section 10.1.3 (b): No Pre-Fetching, Caching, or Storage of Content, before going too much further down this road.
basically, you can't store or save anything that google serves up (like the map image) but you can store your own or user interactions with the map (where they are, if they place a marker, etc) and then display them on a map later.
there's a google tutorial here
that shows you how users can mark locations on the map then send that info to your database