you can get an english teaching job e-z
if you go to tokyo, you can make probably 2,500-3,000 usd a month, but its more expensive to live there
in osaka you'll make closer to 2,200-2,600 usd a month but everything is a little cheaper.
how old are you? if you're in your 20's you might be able to get into the government operated/funded JET program (which is a great start). they'll teach you how to teach, tell you where to teach, subsidize your housing, take care of all your necessities like a bank account, your visa, train passes, etc.
if you go to a corporate school, they dont train as well as they typically look for former JETs to hire and send them out teaching but you can still get into it. don't look into interact at all. ECC is a big one right now. most will sign you up for a 1 year contract and sponsor your visa.
edit: cause im in an apartment with unlocked doors and im fuckin laaaaazyyyyyyyy