Pool Rules

This varies from state to state I am sure. I would ask Fire Marshall or local code department in your area. Your municipal may have a pool inspection department as well. For me no age is "safe" enough to be at a pool alone. Guest limitation is up to the HOA. There may be occupancy limitations. Again Fire Marshall question.

You will get a variety of opinion. None of which may actually be the "legal" answer you seek. Most of the time I see limits of around 12 years old. Another good source is if you have a public pool nearby. See what their rules are and copy them.

From an April 2015 law firm site, https://coultersierra.com/wp-content/uploads/Coulter-Sierra_Newsletter_April-2015.pdf:

"Current HUD opinions for the most part have found restrictions limiting the use of a pool by children under the age of 14, 13 or 12 without adult supervision to be reasonably related to the health, safety and welfare of the child. Any age limitations above that will call into question as to whether or not the concern is over a child being a competent swimmer so much as it is limiting
the use of the pool by children. Please note, however, there are some circumstances where a higher age limit may be acceptable, such as the use of gym equipment or weights. Furthermore, case law involving FHA complaints is constantly evolving so it is important to monitor the current case law to ensure compliance with the FHA."

As for the rule on guests at the pool: For Fair Housing Act reasons, I think it must be age-neutral.