"My age and the cost of school. I have a business degree so I can't just get into teaching. I would have to go back to school for a few years. I can't afford to go."
I retired after teaching for 20 yrs, and I have been a rep for 10 years now (not with Merck). Many states have programs where you can teach while you work on taking classes at night for certification. Teachers with real world experience bring much value into their classroom, and the students really respect that (I taught high school).
As a teacher, I was able to spend a lot of time with my own children as they grew up - priceless. However, as a rep, I make double what I was making after 20 years of teaching, but we never did without what we needed. Pros and cons in everything - your choice. You have options!