These are great examples of how real estate photographers can sell the same photos they sell to a Realtor client for the MLS a second and third time. And you will be a hero in the process. Using three photos to create a standard size post card like the example above is easy, takes only minutes and you don't even have to leave get out of your chair. Once you get some layouts setup you can make a post card at the same time you prepare images for the MLS. I make post cards in Photoshop. Make your layout at 300 pixels per inch (because this kind of printing takes a lot of bits) and save it as a PDF. You will need a PDF for each side. Then login to your printers web site (I use expresscopy.com but there are others- see the resource page just under the blue banner at the top of this page) upload the PDFs and go through their order process and you'll have the postcards in two days or less. Before you make your layout go the the printing site your going to use and find out the details of their layout guidelines.
Real Estate marketing is a very post card and brochure intensive business. We send out between 300 and 1000 post cards for every home we list (unless the market is very fast... in 2005 homes sold before I could get the post cards printed) and we usually send out another 300 to 500 post cards when the home sells. Then 2 to 4 times a year we send out 1000 jumbo post cards to the area where we do most of our business. All these post cards keep the phone ringing with sellers that want us to help them sell their home. It takes 200 to 500 brochures for us to get a home sold. We print our brochures with a laser printer for low and mid-priced homes but for upper-end homes we print them on heavy stock with a glossy surface at Kinko's or expresscopy.com.
I suggest that to make the whole process go smoothly you need to have a limited number of good looking templates so the agent can choose which style they like and then you can just plug in the new text for each new post card or brochure. You don't want to design a new brochure or post card from the ground up each time.
All the Realtors I know need some one to make all their post cards and brochures and they would much rather have the same person do the post cards that does the photography. But for some reason many photographers don't make use of this opportunity.