Depends on the streamer, I followed (not subscribed and didn't donate) one streamer during the first release of Dark Souls 2, for strats on certain bosses and stuff, and you could subscribe and support (an option open to streamers on twitch once you hit a certain amount of followers) to his twitch channel for $5 a month (you also get some special emojis or something to use in his chat), keep in mind that subscribing and following are different. At the time he had close to 1500 people subscribed, 5000 following. He was making approx. 54K (I think he said twitch takes like $2 for every $5 through this) a year off of subscribers ( which has probably gone up since then), and that may not be a lot but that puts you well above the poverty line