When I was in college I did tutoring part-time -- babysitting is also an excellent source of income in my area. My mother stayed at home while my dad worked and made a decent amount of pocket cash from petsitting and babysitting.
It may not sound like the most glamorous of jobs, but if you're already tending to a young one, depending on the type of disability they might enjoy some company with other kids while you can earn some pocket money babysitting.