He does not buy, but begs for zaps... There's many ways to buy Bitcoin (p2p, cex, payment services, +in-wallets integrations), but the minimum amount is always around 10$. Maybe it’s better to save a little in fiat, and then exchange from ten bucks for BTC. Another way is create content on Nostr and stack sats from zaps.
See also https://www.stacksats.how/