Actually, Mandalorians, contrary to popular belief, fill all sorts of jobs. There are Mandalorian dentists, teachers, trash collectors, etc. All the odd jobs that you would consider mundane are performed by Mandalorians who have been raised as, well, Mandalorians, therefore meaning they've received at least basic training in warfare. Nothing spectacular for say, those on Concord Dawn, but enough to fight off any raiders who might sneak onto the world.
That doesn't even include survivors of Junction who know what to expect.