Hello Tim Moore Jr,
There is no hard and fast rule. You want sufficient space for maneuvering which is different for all ages, sizes and abilities. So, go with wheelchair accessible as a minimum to get around.
For room to exercise, I would say six square feet per person as a minimum. For jump rope, hold a rope folded in half and spin around with it for that space, probably ten square feet. For step, go through the moves to decide, probably ten square feet again. Be extra careful and leave more room for kick boxing and such.
You can fit more for the stretching and yoga. It depends what you are doing, obviously.
You must leave extra space, not all people are coordinated the same.
NAPS 2 B Fit