Thanks for the warning. We`re aware of needing to receive permission which is why we really would like to just use photos that have releases "attached" to them already. Or photos that are in the public domain. However, we need really crisp pictures of contemporary/modern homes. Not particularly just the outside, but the inside as well.
However, we are preparing to make strategic arrangements with certain companies to provide free advertising in exchange for the release of their images. And of course if they have an affiliate program this could mean an even more beneficial relationship.