I started learning astrology at 8 when my father died, and tarot/playing card divination followed around 9/10. However, I will say that as I've grown into my late 20s, with any number of "Fool's journeys" behind me and still to come, I've been able to expand my study of tarot in many new and wonderful directions -- it just depends on what "speaks" to your experiences and spiritual self at the time. To me, it really isn't so much about age as it is the devotion to the study and open-mind ready to learn. There are plenty of people, whether aged 15 or 45, who pick up the cards and just want a romantic prediction about so and so; the more serious/genuinely curious students of tarot are always smaller in number no matter what age demographic.