[Shasown]

Its unlikely ebay will stop a processed payment, they can stop a payment but only until any problems involved in the transaction are sorted, so even if you are under 18 and they find out, you will eventually get your money. They do random checks verify ages etc but you are unlikely to get caught in one.

There is the possibility they find out if you or someone you are involved in a transaction with complain through the official system. If that happens they will accuse you of internet fraud( making an account you arent entitled to) and ban you for life. Anyone can easily get round that.

In a lot of cases its only when they go to resolution in the event of disputes or there are iffy adverts ebay come down hard.

Why not after this transaction processes or sometime in the future ask your mum to underwrite your account, in other words she will be held liable for your transactions however you will still be able to buy and sell stuff through ebay.