How to make money in Japan

There are many tens of thousands of foreigners living in Japan. And I know for a fact not all of them work as exotic dancers or (far worse) English teachers. So how do these people make money in Japan?

With Japanese fluency and a suitable degree, there are plenty of professional jobs in Tokyo and Osaka working for mostly foreign tech and investment firms. And plenty of bars and restaurants hire the token white guy who speaks Japanese entertainingly and mixes a decent martini.

But for the long term Japan lifers, is there a way to make a decent living outside of being paid to whore your language skills? Excluding writing, teaching, editing, or proofreading jobs, what is there that the 'average' foreigner in Japan can do to earn a living wage?

If you're living and working in Japan, I've like to know what you do to make ends meet (and whether the money you make is enough to live on). Post a comment and let us know where the money is in Japan!