Chances are that at some point while living in Japan, you'll be asked to teach privately. Of course, the idea of extra cash is GREAT, not to mention being your own boss, choosing your students, and getting paid right away. You can also wear what you want, make your own schedule, and you don't have to worry about adhering to a dress code.
I don't need to go on about the pros of teaching privately, but I admit that potential cons didn't even dawn on me. I don't mean to burst your bubble, but there are things I wish I had considered or that other teachers would have told me about, so I wrote a post a few months ago with advice based on my nearly 5 years of experiences - http://www.trekkingwithbecky.com/teaching-privately/
Good luck, and happy teaching! Give me a shout any time if you have any questions! :D
Twitter - @trekkingbecky
Instagram - @trekkingwithbecky