Here's a photo related product that real estate photographers can easily sell or just include along with a shoot. The product is "Just Listed" postcards that let neighbors near a new listing know that the property has come on the market. The point of the postcards is to get the listing agents face and name in front of the neighborhood and to show them what kind of job that agent does marketing a property. Agents that do this well and repeatedly can significantly increase the number of listings they get in a neighborhood. It's called "farming" a neighborhood. Listing agents do better if they are recognized as the specialist for a given neighborhood.
If you have the photos of a newly listed property and you've done it once or twice, creating "just listed" postcards takes a few minutes, you don't even have to leave your computer and it's a huge benefit to the listing agent. You can either supply the client with a PDF file that they can use to order postcards themselves or you can order and have the printing company will deliver the postcards right to the agents office. Here's how to do it:
Your listing agent customers may already be doing a diluted form of "just listed" postcards where they send out a generic postcard that isn't customized to the particular property and that doesn't have a photo of the listing agent and doesn't have a simple URL to more photos and information. Being a top listing agent is about winning the competition for the home sellers business. As a photographer you can provide listing agents with photo based products that help them win the competition for the home sellers business. By photo based products I mean, Just Listed postcards, Just Sold postcards, Flyers, brochures and tours.