Age shouldn't be a factor unless that person is completely new to the job. I don't think someone should be paid less because they're younger. They should be paid less if they're less experienced at the job than others. If they are really good at the job, than maybe an increase in pay could be set up. But in most cases when young people are paid less, is because they have less experience.
They will gain more money as soon as they work the job a while.
I think if you're good for the job, you'll be paid well. But if you're new to the job completely, young or old, you should start from the bottom like everyone else.