Make sure to assume negative home appreciation, at least for the next year or two. Look at some of the “monitor” topics in the forums here as well to show that prices are in fact on their way down.
Read up on stories of people who have bought homes recently intending to refinance before their adjustable rate reset. Now a number of factors have come into play that prevent them from refinancing. If they cannot afford the adjusted payment, they either have to sell at a loss or face foreclosure. The housing bubble blog is always good for these stories.