It’s not something that I have heavily researched yet, but it is something that I am generally moving towards as well. For the part, beyond my reading ability, I am really far away from being able to translate anything that is good enough quality and fast enough to be professional. I’m a little lucky that I have a couple years left in school still, so right now I am just doing my own little translation projects that don’t get published anywhere, trying to find a method and develop some sort of ability that is of professional quality and fast enough to be marketable.
Anyways, as I understand it, there are three modes of translations. Translation, which is working with the actual source files and converting them into the target language. Next, there is localization, that is semi-inclusive of translation, but more general. This deals with translations, getting contracts, making sure the product works, etc. Finally, there is interpretation, that pays the best out of the the three. Interpretation is live translations, usually of spoken conversation, and pays usually the best.
As for qualifications, someone else will have to chime in. There is the JLPT, and you can also join some of the various associations that specialize in translation. Otherwise, the other big thing that I can think of is having some sort of portfolio to show your employers. This could either take the form of past works, or you can enter into a competition and try to win an award.
Anyways, here is a couple links if you want to do some reading, otherwise, someone who knows better can chime in, hope this helps.
The Poetics of Translation: History, Theory, Practice
American Translators Association