re: How screwed am I by not putting down 20% on a home purchase?

Regardless of how much you put down I'd encourage you to pay extra each month especially if you will only be there around 5 years. Like others have said the cost of selling might eat up all of your equity. The first few years of a 30 year mortgage you're not putting much towards the principle so you don't build much equity. In 5 years you could find yourself upside down on the loan and feeling stuck there or having to do a short sell just to get out. These are scenarios where you can get yourself in trouble if you're not careful. If only staying for 5 years your should consider a 15 year mortgage with 5% down. That would ensure you are paying towards principle. I learned from experience. My first home I did an 80/20 loan with zero down. I paid down the 20% in about 2 years once I realized what a bad decision it was. I'm in great shape now. Just don't buy more than you can afford. I'd say whatever you get approved for buy 20% less and pay that extra towards principle. You thank yourself 15 years later.