First up, yes you can teach in many countries without a teaching qualification, but to get the better jobs you'll need at least a degree.
Why do a teaching course? The main benefit is you get lots of experience of lesson planning, and on a course like the CELTA you'll soon be told where you're doing great, and where you need to improve.
I'm currently doing the CELTA, so ask any particular questions you might have about this qualification. I also started (and might even finish) my basic 120 hour TEFL course, which cost me £175 (less than $300 I guess) including a weekend face to face 20 hour course.
The first thing I'll say is that after speaking to a few CELTA students now, if you can do the course part-time, then do it! The intensive course is exactly that - intensive! The intensive newbies had their first class today. This time next week I expect to see them downing the expressos like crazy when they get into school
