Complex sentence: David Berkeley started showing a passion for singing while still in nursery school: the woman taking care of him when he was four was an Avon saleswoman; she would bring him with her while going door to door, and he would sing to her potential customers.
Split into simpler sentences: David Berkeley started showing a passion for singing while still in nursery school. She would bring him with her while going door to door, and he would sing to her potential customers.