I, personally, have two: one on my shoulderblade and one high on my thigh, near my hipbone. I didn't get either until I was in my late 30's as I wanted to be sure I wouldn't regret my choice of design. Also, as an accountant, tattoo's aren't really considered acceptable conservative decoration

. I love them both and plan to expand on the thigh one (it is a butterfly). Neither one can be seen unless I am wearing a swimsuit or naked (which I'm pretty sure won't happen at work). For me, these were symbols of freedom from an abusive marriage - the first I got as I was working on my escape plan and the second after I made it out (alive).
My former stepdaughter began begging for a tattoo and piercings at about age 13. Her dad and I said NO, NO and NO!!! Finally, at age 15, we told her she could get piercings done as long as they were not visible on her face. She got her tongue and belly button done at age 16. We insisted that she not get any tattoos until she was of legal age as she was too young to know what she would want to live with for the rest of her life. She just turned 24 and finally got her first tattoo (yeah Pangloss61, across the small of her back).
Nothing permanent (or visible) until they are of legal age, is my opinion.
Stormie