I use to be one of those girls in the youth. center. They are not offical staff and are not paid by the cruise lines. You receive a free cruise in exchange for your services. When I worked in there, you had to pay for your own arifare to the ship. The only pay you receive are the tips.
So as a former girl in the youth center - I thank you for the tips. My experience there made me a cruise nut. It was a great way to take a cruise during my college years, when I couldn't afford the luxury of cruisin as a paying passenger.