In many cases the expenses associated with buying them mean the margins are tight.
Start by buying candles, oil lamps, a camping stove, barbecue, and a wood-burning rocket stove if money is tight. Anything above that can bring on flourosis or poisoning. https://companyspage.com/story3087365/10-strategies-to-a-long-life-and-great-health-back-on-the-basicsype-html