Pay after delivery has no use in buying digital goods.
When buying artwork, you are paying for goods and services, so that is the option you should choose when you are sending money to the artist. There are fees involved that the artist is responsible for paying. Some artists still demand that buyers pay the fees even though they know it's not allowed. That is where a lot of confusion starts with the fees. Most artists work the fees into their art so that the buyer doesn't have to worry about it.
It is ill-advised to send as friends & family when paying for artwork due to the chance the Artist could be banned from PayPal and/or fined up to $2,000 for avoiding fees associated with offering PayPal as a payment option.
You do not need any money in your PayPal balance to start buying artwork. All you need is a debit/credit card or a bank account attached that gives you access to funds elsewhere. When you go to send money to an artist, it will ask if you want Paypal to take the money from whichever you have linked to your account.
It sounds to me like your account is already set up and ready to go.