I dont know if there is are age limitations or not, but I can tell you about my own experiences with the prepaid master card. I got one for the same reasons, to buy on ebay, and also to pay my bills with out having to get a bank account. It has been very convenient. And should be a great credit builder and learning tool for a young person such as your self. You can not spend too much by going over your limits, but you are still buying with plastic. There are no crazy outrageous interest rates pay, although you do pay like $1.00 or $2.00 fee each time you use it. But the fees are way less then the interest rates of most cards. For online buying it proves to be the perfect solution, especially for those with poor credit, such as myself.