If you’re teaching violin or viola, it probably makes sense to settle somewhere with good school music programs or a community that’s into private lessons—places with orchestras or a solid arts scene are usually a good bet.
You’re right lesson rates don’t always keep up with the cost of living in the bigger cities. You might want to look into mid-sized areas like London, Kitchener-Waterloo, or Hamilton they still have strong music communities and enough population to find students, but housing is more reasonable than Toronto or Ottawa