Ideally, you should take a CELTA, Trinity, or TESL Canada course. If you are going to take a 100-hour or a 120-hour online course, you shouldn't pay more than US$300. These are introductory courses for people who want to travel and are not sure if they want to pursue a teaching career for the long term, but they can be helpful as long as they cover the essentials in grammar, phonology, and methodology. It's important that the course you take covers lesson planning thoroughly so that you learn how to prepare real lesson plans. Many courses ask you to submit short written assignments, which are easy, but won't help you to become a good teacher.
On-site Trinity and TESL Canada courses in Toronto, Canadahttp://www.study-at-coventry.com
Online courses recognized by TESL Canada and ACTDEC UKhttp://www.ontesol.com