Real estate agents have to be careful not have duplicate content in their websites. Pages with duplicate content hurt your listings' rankings in local search engine results. There may not even be much competition, but your listings' rankings will hurt because of duplicate pages.
If you publish the same story on your website and in another website, then it's a duplicate content. If you have a template where you do your property's description section and lots of sentences are same or similar, then it's duplicate too. You have to either improve or remove these pages (Google generally recommends to improve instead of remove) from your real estate websites or blogs. This refers to mortgage or home improvement websites as well.
Now what has changed?
Recently Google changed the Google Maps layout, and I wrote about its effect on your listings here. Now that made finding duplicate content much harder.
If you went to a search engine consultant and asked to find duplicate content in your website, he or she would go to Google Maps and do a "Map Maker Phone Search." That would help him to find duplicate content in your listings or website. Now the phone search in map maker is gone, making it much harder to find duplicate content on your website.
Google has made this change for several reasons, and this is well discussed by Linda Buguest at Local Search Forums.
What Do We Learn?
Make every effort to avoid duplicate content when you are writing a house description, when you are writing a title for your property listings or when you are writing new blog posts on your website.