So within the Ontario Day Nursery act we can only have 5 children plus our own at one time, and I understand that if theres a little overlap you may consider whether this is a risk worth taking incase you are found out and get in trouble. Each to their own in this scenario, although I do believe their are rules in place for a reason. I also know that in Alberta you are allowed 6 so Its not a factor of whether one more child is to many or not just the individual provinces have different guidelines.
What I want to say that is WAY more important than this rule, is INSURANCE!! There are but a handful(if that) Insurance companies in Ontario who will allow 5 plus your own to be insured so the chances are your 9 year old would not be insured. I flat out say don't do it. If ANYTHING happens, you are screwed. You would be ruined if that parent took legal action, or even slandered your name around your neighbourhood.