Depends on the singer and if they feel like doing a sweet sixteen private party or not.I would say what they would take in for their personal fee for a concert.they may even do it for free if it is attached to a charity.in other words people pay what they can afford or are willing to give to help say find a cure for cancer/ms/heart disease/what ever floats your boat.maybe a concert in a park.since I don't know where you live I can't give specific details. A place like central park would be a great place to hold a charity event.or a local baseball stadium in the off season.that way the stadium out of the goodness of their heart could hold the event and write it off as part of their donation to the event.now if you really want to know what they would accept for a fee to appear at a private party you would have to contact them or their agent in order to find out if they even have time to do a unplanned event like a sweet sixteen birthday party.just my guess.