If you and your spouse are financially secure, you might try doing the work you want to do, but for yourself. Create medical illustrations and put them up on your own web site. Or publish and distribute them as a zine. If you can find a way to offer something that is useful to others you may even be able to sell it. If not, you are at least doing what you want to do.
I've done this in education and toy making (
http://www.foreworks.com,
http://www.flamingsparrow.com) with enough success to keep me fed, housed and happy. I've also had my creative writing needs fulfilled by being the staff reviewer for a national sports magazine - at crap pay, but I got business cards! Fortunately, I merely have obsessions that I learn to monetarise. I don't have a calling.
I realize that I'm very, very lucky. Being a "success" is rarely a matter of simply wanting to do something badly enough and working hard, especially in the current economy.
I hope you realize that there are only a dozen medical illustrators who consistently get work. Everyone else gets temp job or occasional piece work. Apprenticing is a 20-year process, minimum.
My wife is a trained, degreed, and highly experienced graphic designer who has done some medical illustration. She's also done graphic production finishing for Apple (the last step before they go on Apple's web site) and designed all of the display and logotype for the opening of the San Jose Tech Museum and for Stanford's campus transportation system. But right now she can't find work near home either, so we may have to move far from silicon valley for her to get work.
We may wind up in Louisiana, living rent free in her retired parent's large and paid for house, where my now meager income is sufficient keeping us going while she tries to set up a design business and a studio in which to teach. That may even be the answer to our dreams, but we won't know until we try it.
You do what you gotta do and what you can do, and it's
always a compromise with what you want to do.
That's not very hopeful or helpful, but it's what I've found to be true.
I wish you good luck.