Both Venus (67 million miles from the sun) and Mars (141 million miles from the sun) fall in the Goldilocks Zone for our star. If earth were to trade places with either of them we would still have liquid water on the surface of the planet. While life would almost certainly be different - it would by no means be "impossible".
The biggest differences between our sister planets is atmosphere. One has too much and the other too little. Though in a few hundred million years Venus volcanic activity may calm down enough for the planet to support life. And Mars once had oceans on its surface - possibly even life.
Our Sun if over 4 billion years old. And will likely run another 5 billion before swelling into a red giant. The current state of our planet is but a snapshot in time.
Even more destructive to the Creationist's arguments - we now know liquid water can form absent the necessary energy of a star. Both the moons Europa and Enceladus of Jupiter and Saturn (respectively) have vast liquid oceans.