You're free to do what you want, but I wouldn't want to be caught in a situation where something went wrong with the transaction - either with PayPal or with the sale. Trying to get help from your parents, especially since you're probably living under their roof, without having an "I told you so" conversation with them wouldn't be something I'd want to do. I'm sure you'd be able to find another seller that's willing to take a credit card number over the phone (which is exactly what prepaid cards are) that won't involve sneaking around your parents.