Could you get extra money doing other things? You're a teacher, could you tutor on the side or coach a team? Could you work one longer day instead of two days, thus giving yourself a day off? The good thing is that if you did start working selling cars, you could always quit if you weren't happy. The key, I think, is that you make sure that you keep a promise to yourself to quit if the cost is too great. Everyone has a tendency to accept the inertia of staying in a job that is taking a toll on them, don't let that happen to you.