If the item sells, there will be 2 emails from Ebay to your son's registered email address.
One confirms the sale and one conffirms payment.
Looking in 'orders' when logged into Ebay, you can also see if items have been paid for or not.
New sellers, particularly if they sell high value items can be subject to payment holds of up to 30 days before funds are released to them and of course your son does have to regisater his bank account and link it to his Ebay account.
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)