I'd say affiliate marketing is more of a modern "lemonade stand" business, just like youtube/twitch videos, game programming, and app development. There's an extremely low barrier to entry and it gives you an ideal place to hone business skills, but odds are you won't make enough to cover the cost of hosting a website.
My impression is that, if you find a niche, stick with it, and do at least nominal marketing, you'll make a few bucks. But emphasis on few. For most people, it's more akin to a nice hobby than a real business.
