Bringing in the second instrument/stave at a appointed time.

Hey everyone, I am writing a piece for Piano and voice and the introductory 4 measures is pure piano with no vocals and I want to have the first system be just the piano with the voice coming in on the next line/system. I am doing this to save space and because I like they way the piano/vocal scores from Alan Menken look. I am studying his scores and song structures. I would like my score to look very similar to the attached picture. Thank you.

(thanks to Shoichi and Jo-Jo Schmitz for helping earlier today).