Applied at Hyundai dealership for car porter

I recently interviewed for a car salesman position at a Hyundai dealership, but the manager offered me a full-time car porter role instead, paying $17 an hour. He mentioned that after three months, he might consider moving me into sales if my performance is good. Currently, I work as a substitute teacher, making $22 an hour with a flexible schedule, which is great for my full-time college classes. I'm torn about whether to accept the porter position or stick with my current job. I really want to become a car salesman, but I also value my current pay and flexibility. I’ve been getting mixed advice, with many suggesting I shouldn’t leave my job for a lower-paying position that may not lead to sales. I’m really weighing my options here.