It would be much more of a time commitment than a money commitment for you. I went to grad school for CS part-time while working full time, and it was a hard slog at times. In the end, I decided not to finish the degree--I was learning the things that I wanted to learn through my job, and also I was starting a family, so I had much less flexibility to get to campus and to juggle work, school, and household all at once.
But before I quit, I was thinking of choosing human factors for my minor--interesting, fun, and potentially useful.