As a Realtor, you may want to get rigorous in optimizing your marketing efforts on Facebook to develop the largest audience. As your audience gets larger, it will naturally grow faster. The larger it is, the more incremental business you'll gain.
The best way to get shared beyond your immediate graph is to engage with people.
This concept is pretty straightforward: Post good stuff and people will share it (by commenting on it, "Liking" it, or explicitly using the "Share" function). Comment on other people's posts, and you'll strengthen your relationship with them and start making an impression on their friends.