There's a book cover artist who's work I'm interested in. It's a sample of her work with a blank field for author name and title. She said that if I buy it, she'll add my name and title to it (I assume that means she'll then submit it to the publisher). Is that common practice for premade work? I'm not sure if I should be saying that she'd then have to submit it herself, and thus get royalties from sales of my book... or if it's a one-time purchase and then I submit it myself?