If you buy a good stock right before a bubble, you can double your money quickly, too (ask me about INTC or CSCO or AMZN in 1998). The point is, what's going to happen under likely circumstances? More importantly, what's going to happen in a rational market?

Home prices are coming down from the largest asset bubble in US history. If you've never thought about homeownership before 1995 or so, you might assume that home prices always increase by at least 5% per year. You'd be wrong, however. Homes in the US are historically an under-performing investment; over the long-term, their returns approximately match the rate of inflation.

There are exceptions to this rule, but I think that the parent comment is generally well-taken: it's not guaranteed that your home is going to double in value in five years. (In fact, in some parts of the country, there's a real chance that your home will be worth 50% less in five years' time.)