There's quite a bit in the news at the moment about dodgy TEFL courses. Indeed I know that in Taiwan and China (probably like many other countries) some westerners don't bother with any accreditation at all and assume that they can teach English just because they can speak it. Of course, this is not recommended!
So I've had a quick look into this and found out that an accredited course is not that expensive, even for a gap year student. Course organisers like www.onlinetefl.com can provide an online course and also set you up with a job abroad. You can even get them to call you first (whichever country you're in) to discuss what qualification you're interested in attaining.