There are two fairly large, rectangular areas that are now used (sparingly it seems for the time being[he says it "gets busy" in January and February]) as driving ranges. Either, or both could be used for fielding and throwing work, or perhaps for indoor pitcher-catcher-infielder competitions. I would have to re-turf it though, the present rug is pretty beat up.
I would want to offer instruction. Understand that in my neck of the woods there's lots of opportunities like this. I would not be under pressure to feed my family from this enterprise. it would be strictly a part time gig for me.