The thing to remember is that with all English teaching qualifications, schools will insist on classroom teaching practice. An online TESOL isn’t much use without any classroom practice. Preference will usually be given to experienced teachers. However, native English speakers already living overseas can often be offered jobs teaching English there and then, provided they have a degree.
The other thing is that your English teaching certificate should be for a minimum of 100 hours otherwise schools will be reluctant to take you on – so forget about doing any weekend courses. Always opt for a 4 week English teaching course.