"Unless there is someone willing to buy, and someone willing to sell, the MMs cannot make any money and there won't be any volume. MMs don't have a "stash" of stock available to sell"

Yes MM may have stock to sell or buy to accomadate trades.. thus make money!!!

market makers, routinely take positions in stocks, both long and short, and then turn them around for a profit, or a loss, later in the day. They provide liquidity, but they are also more focused on capitalizing on your lot of stock by buying it for their own trading account and then flipping it to another buyer. In any case, market makers will sometimes post phony sizes in order to lure you into buying or selling a stock.