Royalties will sneak up on you. First you get that wonderful advance. Next it has to earn out. At 10% of cover for each book sold, that will be tough.
Let’s say you get an advance of 100,000 (yeah, right, Jeff gets more than that? we’ll use th is for easy figuring). Say your book is hardcover, and retails at 29.95. that means, for each book sold, you get 3.00. But if you have an advance of 100k, you see no money until enough books have sold for your $3 royalty per book pays back the 100k. that’s 33,333 plus books, Jeff. Hope you’re selling that money.
I’d give another rant about mass market paperback and reserves against returns, but it’d end up tl;dr, and I don’t want to drive everyone nuts lmao.