They set out to create characters and plots and withhold the dramatic purpose of their stories until page 41 or beyond. It means they've taken forty pages to get to the first sentence of their story. Blatty begins his story with the first sentence he writes. The first sentence of the second paragraph, and two additional words, The house was a rental. So he picked the single word that met his dramatic purpose.
Many inexperienced writers struggle because they set out to make and prove statements.
None of those statements would advance the story itself. Again, Blatty only uses those words that via their arrangement and design advance his story, and he has a guide to chose those words from understanding his story's dramatic purpose. Even the ivy is apparently disturbed by its association to this house. Blatty always offers significant details that pull his audience deeper into his story's world. Again that accurate use of words that are suggestive of a place where this battle between good and evil will commence.