Some native speakers without any formal teaching qualifications find teaching jobs, and a few of them turn out to be reasonably good teachers. However, unless they are simply going to have informal conversation classes with one or two people at a time, most people with no qualification give a pretty poor service. Even the month-long CELTA and Trinity course, the only ones really recognised in Europe, claim only to be beginning qualifications.
95% or more of the trainees I worked with when I was a teacher trainer were pretty useless as teachers at the start of the course.
Many non-CELTA/Trinity courses are actually quite good - and some are appalling!. There is unfortunately no way of being sure. The fact remains that many reputable schools will accept you as a beginning teacher only if you have a CELTA or Trinity CertTESOL. If you wish to work for yourself, then it is possible to find students who don't worry about formal qualifications. Whether you work this way and give value for money is for you and your conscience to decide.
Whether or not teachers should teach grammar formally to people who wish to learn to communicate in the language is something about which there is no general agreement.. However, even if you are a fan of communicative approaches with no formal grammar, you will find that many of your learners are use to having grammar explained, and will demand answers to questions about grammar. Even if you decide not to teach grammar formally, you will find that you need a sound knowledge of grammar in order to be able to present structures meaningfully.How important is the grammar?
What you teach your learners and how you teach it depends on their needs. If they wish to pass some internationally recognised examination such as those offered by Cambridge or TOEFL, then for the higher levels, they will need to have a sound understanding of reasonably formal English.Are we to expected to train the students to write at journalist levels or something?
If you are teaching children, whose future may depend on their English language skills. you have even more of a responsibility to make sure that you know what to teach and how to teach it. Note, too, that teaching children is usually far more demanding than teaching adults. CELTA, and many of the other courses on offer are designed to train people to teach adults, and are not very useful for people who wish to teach children. There is also the point that many state schools will not employ teachers without a state-recognised teaching qualification; the month-long courses, including CELTA, are not state-recognised.I don't really care about being a teacher in a prestigious tier one school abroad. I would be extremely happy just to be teaching children in a cheap suburban school in a small city/town.
It seems to me that your main interest is in finding an escape from life with your parents rather than in teaching. You may be able to find teaching work - some untrained people do - and you may even be successful. However, I think this is unlikely. Most people who wish to learn English prefer to be taught by people who have a real interest in, and some real knowledge of, both teaching and English.