My husband when he had a good sewing machine made quite a few headstalls and chinks/chaps. His machine didn't sew think enough to make thicker stuff like hobbles unfortunately and he sold it when we moved to TX. We plan on buying another in the spring when we move home.
Anyhow...he learned from apprenticing with other makers. Good quality stuff like lined, stitched with quality silver headstalls will sell. You can't compete with Pakistan and Mexico for the low quality crap. Finding a niche seems necessary.
Finding a wholesaler for your leather is helpful rather than paying full price. We also buy the silver wholesale or have it made and the prices reflected either way.
For patterns, we found that buying a good quality headstall or what ever, take it a part, and tracing the pieces on some tag board is the best. Most makers won't give up their patterns if they think you are going to copy and sell. Tandy Leather sells patterns, but they do need a bit of adjusting to make them workable though.
I DON'T LEAD 'EM AND FEED 'EM, I RIDE 'EM AND SLIDE 'EM.