1) Pretend you work at one of the big agencies in NYC, some outfit from page one of www.everyonewhosanyone.com , Trident Media or William Morris or whomever. How do you get paid? Are you on a draw? Any rough idea what the split is with the house?
Nope, not a clue. Miss Snark has never worked at any of those places and hasn't yet asked how her friends can afford their bar bill.
2) Talk to me about joint accounting. Only bestselling authors can have each book stand on its own, right? Or does that vary from publisher to publisher?
It varies from publisher to publisher and on how the books are sold. One offs are generally accounted for one by one. That is, I sell a book to Publisher Z and Z sends royalty statements on that book and only that book. If the book fails to earn out the advance, their loss.
Joint accounting is the concept that books are bundled accounting wise: if you sell book A and book B to the same publisher, the accounting is on one page. Most important, if A fails to earn out the advance, and B is making money hand over snout, the publisher can use the revenue from B to "top off" the account for A and make it break even.
As you might imagine, this is not a concept I like. There is no up side for the author. Generally you don't run into this in a contract unless you have a multiple book deal on one contract, or an option. I negotiate them away with vigor. Publishers love them cause it's another shot at not losing money, the greedy beasts.