is it illegal to have an ebay account if you are under 18?

Answer 1

Yes it is illegal. Why is it illegal? Simple, you must be above the age of majority (18 most places, 19 in others) to enter a contract. Everytime you agree to sell or buy an item, you are entering a contract. Most of the time, you selling things at a garage sale or to your friends is no big deal, that can change when the deal involves going across state lines.