Of course that is true, but mortgages have options to make regular balloon payments and such. You can "catch the train now" and beat that problem down later. If you're young and starting out in a good field, you can expect your income to rise.

How much you're going to pay and how long it will take is just a projection based on the current numbers: interest rate, remaining principal and payment size. The projection isn't reality.

Indeed! The only time putting little down makes sense is if interest rates are low (they're currently at historical lows, and the Fed is starting the ratchet to move them up) or you're sure there's going to be significant appreciation in the value of the property to overcome the expense of that interest.