[MMM]

I would move to Japan to learn Japanese better (it's the best way, for sure), but I wouldn't move there to become a translator.

If you are a native English speaker, you will be translating mostly J to E. Japanese publishers in Japan don't publish books/manga/etc. into English. That is done by overseas publishers that buy the rights and then translate the stuff...usually "locally", but not necessarily.

I did do work for the Tokyo Metro Government translating part of their website into English for foreigners living in Tokyo, but that kind of work is (obviously) not very steady.