Do you speak English? Do you like money? Do you enjoy talking to interesting people? Well, have I got a job for you!
You, as an English-speaker, are in possession of a very valuable commodity. People from other countries are more than willing to hand over big chunks of cash to hear you speak. That is right; you can make money by teaching your own language! Moreover, it is not difficult.
This business is best if you live in a high immigrant area or a university town, but it can work anywhere there are people who don't speak fluent English. Choose your target audience, Korean, Chinese, Indian, etc. and find someone to help you write a sign in that language. Better yet, in all languages that could be useful in your area.
To eliminate those who want $1 classes, list your price. This will vary depending on where you live. For individual classes, you can charge more, perhaps $25-35. If you feel up to teaching a class, keep it small, max. Five or six people and charge less per person, $5-10 is appropriate.
If you have no interest in grammar and do not care what a gerund is, you can offer conversation classes. These require minimal grammatical explanations; their main purpose is to offer practice and pronunciation. For those grammar lovers among you, offer a full course, with reading, writing, grammar, and conversation.
There are plenty of great English teaching books out there, but my favorite is the Cambridge University
