I use OBS software to stream on Twitch and here are a few links to get potential streamers up and running.
Open Broadcaster software
https://obsproject.com/
Setup guide for OBS
http://help.twitch.tv/customer/en/portal/articles/1262922-open-broadcaster-software
OBS Setup video playlist
https://www.youtube.com/playlist?list=PLzo7l8HTJNK-PP70gT9lLmHokkRrQqer2
Slightly older setup guide (the one i learned with)
http://liftgaming.com/2014/12/obs-setup-guide/
I also use a logitech c920 camera for when streaming my cab
OBS can seem a little daunting at 1st but there is lots of help out there to get you streaming in no time.
Hope to see more 'Vac guys streaming. It is a lot of fun.
And, you do not need a beast of a pc to stream with. I use a core2 quad from 2008 and that streams in 720p no problem.
As far as paying monthly for a Twitch account, I haven't and I use an adblocker
to remove ads. Never had a problem with my streams.
If you start
to like streaming you will probably want some emotes for your chatroom.
The most popular emote add-on for Twitch is Frankerfacez (ffz for
short)
http://www.frankerfacez.com/
And once you get a stream setup and running, you can check the streams quality using ths analyzer
https://r-1.ch/analyzer/
A Handy app for keeping track of who's actually streaming with alerts is Twitch Now: for chrome
https://chrome.google.com/webstore/detail/twitch-now/nlmbdmpjmlijibeockamioakdpmhjnpk?hl=en
For Firefox
https://addons.mozilla.org/en-GB/firefox/addon/twitch-now/
A
final note on streaming. Dont set your broadcast bitrate to as high as
possible (noob mistake). Start with a low setting and work your way up
to find a stability / quality balance. If you stream with a high
bitrate, its harder for viewers with slower internet to watch.
I
stream in 720p with a bitrate of 1500 and it looks good enough. My pc
runs at around 15% cpu, with mame, twitch, obs and a music player all
running
Unless you are a Twitch Partner, the stream you send into
Twitch is what they feed to viewers. Twitch Partners get "Transcoded"
so that streams can be watched on tablets / phones etc. I've seen loads
of streams with stuttering video set to 1080p and 3500 (max) bitrate.
Bigger is not always better.
Hope this helps.