you're allowed to get a piercing done when you're 16 and anytime before that under parents/guardian permission. (if I remember right)
Most workplaces are strict on piercings (as with tattoos) and do not allow them to be seen, even tongue piercings can be seen when talking.
My piece of advice is to get a piercing that you want a long time before you get a job and allow it to heal, that way you're able to go to work without having a ring in (so it doesn't close up) if it's in you're ear they'd probably let you get away with a clear plastic stud...
ummm that's all i can think of for now, if stuffed up explaining something let me know and i'll get back to ya