First, congratulations on your plan. You sound like you are really looking forward to it.
As you make your plan, I just want to add a note of realism from my experience.
I don’t know anything about what kind of shape you are in, but you mentioned arthritis and injuries, so …
I teach dance, TRX, and the LIVESTRONG program at our local Y. When I first started teaching, I was all “Woo hoo!” Then I found out my body had limits. I could only sustainably handle about 2.5 hours/day of classes where I was instructing by physical example. I tried 3.75/day for a month and it trashed me.
I bring this up because you might want to think about the number of hours you want to teach and how that will affect your income.