normally, it is appropriate for kids to ask for money from their parents, even if they are 18 AND still lives at home. which is usually considered borrowed money, or time. which means, the repayment can be in the form of currency or labor around the house/yard.
what happens at their home, is really their business and no one should be investigating it.
whats not appropriate, is this person telling (guiding, would be a better word) the 17yr old that it is appropriate, as I do not see the gain of the 3rd party/outsider.....so i will assume there is some form of a gain for the outsider.