Having some cash around is a good idea, esp. if you're buying a new house. If you don't have any sort of emergency fund and you still want/need a house you might want to consider putting 10% down instead of 20%. Yes, you'll be stuck with PMI and that's pricey, but having no cash when you need if can be pricey too. (Of course, if you have an emergency fund or even willing parents who will help you out in a bind, not paying PMI is good too . . .
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