Each of the colonies needed private citizens to be armed and available for defense (the militia) because there weren't enough British army troops to adequately defend the citizenry against hostile Indians. That's where the argument comes from that the 2A applies to the National Guard and Reserve. These militia joined the Continental army which was formed to fight the Revolution, after which the Continental army was disbanded and the militia - the "Minutemen"- were all the nation had in the way of land-based military capabilities to provide defense against hostile Indians. Everyday citizens (all fit males between 16 and 60) engaged in a variety of professions would be called to military duty in the event of an emergency, bringing their personal firearms. That's why the first part of the 2A reads like it does. About 2 years after the Bill of Rights was ratified the Congress formed a standing Federal army in order to provide better defense of the citizenry against the Indians, a role the British army of course wasn't going to fill any longer.
In those days some of the guns used for hunting, which just about every household did, were not all that different from the ones the military used. The civilians had smooth bore shotguns which were very close to the Charleville muskets they got from the French and Brown Bess muskets from the Brits. The civilians also had smaller bore "Kentucky" rifles that were much more accurate that they hunted with; these and the smooth bores were what the militia would bring with them when they were called to duty- their personal firearms.
Despite the cost of living, have you noticed how popular it remains?