Talcum powder comes from the crushing, drying and milling of mined talc rocks. The substance is mainly comprised of magnesium, silicon and oxygen, and the particles are extremely small so therefore they can easily be inhaled. For any lungs this is a problem, but for the tiny lungs of a baby, it can be particularly irritating and can cause inflammation. As a result, the American Association of Paediatrics recommends that parents do not use talcum powder on their babies.
Nature's Baby Organics Silky Dusting Powder is safe and gentle enough for all infants, even newborns. It is made out of nothing but USDA certified organic ingredients, including tapioca starch, and organic extracts, including matricaria flower extract, echinacea angustifolia extract, and goldenseal extract to further soothe and calm irritated skin. Simply dust it over baby’s bottom to absorb wetness and relieve chaffing.
There are resources available to you if you need them, though. Also, don't discount cloth diapers if you have the means to launder them. They're often easier to get at free or reduced cost, not to mention they're way better for the environment, and you can be super smug about that. (Unrelated, but once you're done diapering your baby, those diapers really make the best dusting cloths and glass cleaners.)
A nationwide network of clothing closets can be used. While some of them sell low cost goods, others will provide the essentials that a new, low income parent needs at no cost to them. Some struggling families may be given help for a newborn, or free diapers may be offered in an emergency. They also provide referrals. Find sources of free clothes and household items.