Would the best way be, then, to scale the effort as resources allow? Learning to make your own fire is much cheaper than building a fallout shelter--next in line might be a survival kit (including matches, lighter, and flint, in case you find that you are incompetent at producing fire--like me). I've grown the opinion that all people should have a basic survival skill-set; it would be pitiful to have to rediscover animal trapping and such.