The Chicken or the Egg?

We are jumping in the deep water talking about DEMOS and this is PART ONE of a multi part series of at least 3 episodes about DEMOS. When, what kind, how much... no wait, do I need to BUY a demo?  Who should I hire?  How often do I change it... REMEMBER... THIS is the Voice Over Rookie phase so buckle up sweep pants... we got a few answers or opinions for you!