The only guidance I would offer is this:
My school has 2600 kids. We have a math department of 22 teachers… and an art department of 3. It’s HARD to find a job teaching art, since there are so few jobs out there.
BUT that doesn’t mean you deter him from doing what he wants to do with his life. (Come on, he’s choosing a profession, not planning to deal cocaine on the corner.) But it does mean that you offer him guidance in ensuring that his choices will eventually lead to employment.
Would he consider minoring in math or science, and getting dual certification? (Check your state board of education to see what it would require. Look at schools that would make it possible.) For what it’s worth, the best job markets in most parts of the country are for secondary math, Chemistry and Physics. Would he consider those as a backup until he can find a job teaching art? Or some other minor that will allow him to work in some other aspect of art-- someone mentioned animation, I’m sure there are others.
In many states he’ll eventually need his Masters for certification. (You can teach w/o it, but only for a limited time. In NY I think it’s still 5 years.) Would he consider a less pricey school now so that you can afford to help him with that later?
For what it’s worth, my husband and I are both teachers in Catholic schools-- so we’re paid less than our public school counterparts. While I don’t know whether you can call us “prosperous” we’re doing OK. And we both love what we do… that’s so important!!!
So in your shoes, I wouldn’t be trying to talk him out of what he wants to do… particularly if you have a rocky relationship. But I would be helping him find schools that have a strong career placement office for art teachers, with a solid recent history of success. And I would be looking for lots of field experience-- you want him to see the realities of teaching up close and personal, and early in his college career. And I would be finding opportunities that would help him have the strongest resume possible.
I know you want what’s best, but he’s going to interpret anything negative about his choice as another reason why you don’t see eye to eye. In the long run, we’re all entitled to our own mistakes. So help him, encourage him, work on the things that will strengthen your relationship.