Your heroine is walking and sees a homeless person. She has an immediate gut reaction and then realizes that the person looks familiar.
Who is it? Is it a long lost boyfriend or someone related to a good friend perhaps?
Why is the person homeless? For example, did they run away as a teenager?
What was her initial reaction? For example, did she want to cross the street to avoid walking by them or was she immediately overcome with compassion and counting the cash she had in her wallet?
What does she do and how does the homeless person react? How does her action impact the story? How does she meet your hero?
Unfortunate statistic – There are 633,782 people experiencing homelessness on any given night in the United States. You can learn more about homelessness in the United States at End Homelessness, http://www.endhomelessness.org/pages/snapshot_of_homelessness. Research for your story, learn how to make a difference.