It is only a terrible idea if you are homesteading with it. That is, you plan on buying and paying off the house you bought. On the other hand, with a lower payment you can get into a house on a smaller budget, then allow the home to accrue some value over time. You then sell that home, at a profit, paying off the 50 year mortgage when you do. You buy a different home with a bigger down and get say, a 40 or 30 year mortgage this time. You allow the home to rise in value, sell it, then buy yet another home. Over say, 20 years, you end up in your 3rd or 4th house with 10 to 15 years left on the mortgage, or maybe, even better, have gained enough equity to outright buy a house for cash and do away with the mortgage altogether.