If you are a musician of any kind, there is an opportunity for you to earn some good part-time income from your skills. It doesn't matter what instrument -- there is a demand for private instructors on all instruments, but especially guitar and piano.
Your first thought will probably be "But I'm not qualified!". That's exactly what I thought many years ago when I started, but necessity demanded that I try, and by taking beginners only at the start, I gradually learned what it took. There is an endless supply of beginners looking to play an instrument and its a supply that is inexhaustible.
Of course, you want to get qualified as soon as possible, so simultaneously take some lessons or instructions yourself. I was in college when I started, studying music, and many of the questions I had got answered by the teachers I was studying with myself. By the time I got out of college I had a "one-person music school" that later bloomed into a multi-teacher studio.
For information on starting your own one-person music school, click here.