Travel is one of those things you can do for free if you really, really want to. Hitch hiking doesn't cost anything, so you can travel all over North and South America if you've got patience, thick skin and a willingness to take risks. I've a buddy of mine who did just that. Started in San Antonio and is now in Argentina, if I recall. He's not poor, so he could do things like hire a boat to get around the Darien Gap rather than stick around and try to work to get enough money for it.

But even if you're poor, you can always find ways to make just enough to scrape by. I met guys while I was traveling that didn't have a dime but yet still managed to get around and even have fun.