Back in the early 90s I got a Secondary Education degree with double-majors in English and Mathematics. I went on to get an MFA in Poetry from a well-respected department. But I never got a book together as I found that I enjoyed teaching almost more than I enjoyed writing. But after a two-year instructor position wrapped up, I was unable to find a full time English position; since I feared trying to live on a part-time instructor salary, I had to look outside academia for something else and I've would up selling cars for the last seventeen years. But I was laid off very recently and now I think I want to get back into teaching. English positions are few and far between, but I notice all kinds of advertised Mathematics positions. Is it crazy to think about a PhD in Mathematics Education at age 46? I don't even know who I would have write letters of rec for me... Everyone who knew me as an undergrad or even as a grad student--well, that was 20+ years ago. So where do I start? Is this possible or pipe dream? Any thoughts would help...
A PhD in mathematics education is a highly sought after qualification these days, although it isn't clear to me whether the long term prospects over the next 20+ years are particularly good for any academic career.
Getting a PhD late in life is certainly possible- two of my colleagues in a relatively small mathematics department got their PhD's in mathematics well into middle age after other careers.
Given that you got your bachelor's in math more than 20 years ago and haven't done anything in mathematics since then, you may have some difficulty doing mathematics at the level you were at when you completed the bachelor's degree and without current letters of recommendation you may have a very hard time gaining admission to a graduate program.
One approach that might help you to reestablish yourself in mathematics and get into mathematics education would be to start taking graduate level courses as a part time student.