I just wanted to pose another scenario based on your topic a week or so ago. This has not happened to me, but I can see its possibility.
On that recent subject, you wrote about the problem that someone who has just bought a home is now demanding that all photos be removed for the sake of their privacy. The several resolutions to that problem seemed fairly cut and dry.
Most of us often shoot condos and town homes that are physically attached to another unit, What if the neighbor comes out and demands that you cease and desist from photographing any part of his/her home? I can see that we can argue that the front facade is already publicly visible from the street, but it is not so simple when we start to shoot from the rear and the neighbor's garden/courtyard may be seen in photos.
Moreover, what if the subject home is in a private, gated community? Does this give the neighbor more control over the situation?
Certainly, you can crop the neighbor's home out, but this is decidedly less appealing and can cause some very odd photo dimensions.
The general rule is that if you have permission from the owner or manager of the property documented in a property release (see Carolyn Wright's article on lynda.com on this subject) then you have permission to photograph the subject property. Sure, in some situations you will necessarily include some part of an adjoining property but my guess is that if the main and obvious object of the photo is the property for sale, then you are not going to have a problem.
My non-professional opinion is that the listing agent's listing agreement with the property owner and the fact that you are working for the listing agent is all the documentation of your permission to shoot the property that is required. I've never heard of anyone getting a property release to shoot real estate although if you expect problems from neighbors or have a sensitive situation, it can't hurt to have a property release.