@Emily *******
Recently in the past year they changed the rules about who/what qualifies as a teaching institution. As such some places were only able to secure a 9 month visa, while others were able to do the full year. There are cheap non-credible options, which can cost you the price of tuition, visa fees, etc - and you will not be too much better off.
There used to be tests involved to allow you to continue. I have never heard of anybody failing - but I suppose that can be done.
Also there is the cost of tuition and the time commitment. Some places require that you're in the classroom 20 hour a week or something.
Probably goes without saying - but... Before you make a commitment - try to find someone who has the experience you seek, with same nationality and do it like they do it.