To my knowledge (at my university), there is no requirement that candidates for a master's program have to do any research before entering the program.
Salariman jobs depend on whether you can handle the language (writing, speaking, reading). The pay itself probably depends on the field. What's yours? Look up the classified ads in The Japan Times online or in Metropolis online, or if you can read Japanese go to Career Cross and see what the starting salaries are.