@RebeccaF - Thank you for your insight, experience, and details! I especially appreciate your advice on insurance - that’s a detail I overlooked, and I thank you. I like the terms you set - using when you’re there. I have an outside fire pit, and do the same with that, and also require guests to have the hose on, and nearby should the need arise. Guests have been very good about abiding!
I have a friend that offers/lists an outside hot tub at a shared space. They already had it before listing their space, so don’t claim the purchase, but do claim the expenses of chemicals and maintenance.