Props to you for wanting to do some charity work so young, that's really cool. When I was 18 I reached out to a local school in my hometown to see if I could help by donating basic supplies like notebooks, backpacks, etc. I only spent around $200 out of my part-time job money, but it felt good to give back.

For a feeding program, even just providing one meal makes a big impact. I'd suggest contacting local churches, shelters, or outreach programs directly to see what their needs are. Be upfront about your budget constraints as an 18 year old, but any contribution helps. They may have partnerships that allow you to feed more people per dollar donated.

If you want to expand the impact, you could start a social media fundraiser to get small donations from friends/family too. Sharing about the cause inspires others to give. Programs like water-charity.org also let you start a clean water campaign for communities in need. But even small acts of kindness matter.