Fibromyalgia and back & neck problems don't play well with the idea of sewing for a living.
The availability of cheap clothing from WalMart has just about done away with tailor shops and custom clothiers.
A woman I know makes western shirts from a basic pattern and fabric supplied to her, then mails them back to someone who decorates them with a lot of "bling" and sells them at fantastic prices. The lady who makes the shirts gets paid very little.
My sister was an excellent and fast seamstress. She made far more money doing custom sewing for an interior decorator than at her day job. Many times someone would ask why she didn't make wedding dresses, etc., and her stock answer was that a sofa cushion didn't gain or lose weight or have personality issues. The decorator would give her the fabric and an idea of what was desired, and she got paid, very well paid, on delivery.
If you're set on sewing clothing, I'd think that re-enactments would be a good place to test the waters.