Accounting is not really about math; it's arithmetic, adding/subtracting, but the accounting concepts themselves are what's complicated, and I don't know that a single course will qualify you for much, job-wise; I would just take a bookkeeping course and see if you enjoy it; it would help you keep your own books if you do start up your own shop. But if your doctor told you to get out of the cooking industry, doesn't that include somehow starting your own shop? That's more stressful than the industry itself as you have to be full-time worker and deal with all the other business parts as well, often a more than full time job; you'd need a whole business degree practically.

I would try to get a job with a caterer or small shop, SorryShape's idea of a food truck is good, etc. and see if you'd enjoy that and it would be comfortable enough for you and your doctor and learn on-the-job and see what you might need in school or how to move forward from there. I think just taking a random class, currently unrelated to what you have in mind and how it might help, etc. might be more frustrating than helpful?