I`m the one Craig mentioned who does home portraiture.
People who commission personal art (portraits of themselves or their homes) like knowing the artist. It`s an emotional purchase, thus often requires interaction between artist and buyer. This whole idea of subcontracting through photographers and people not knowing you exist sounds detrimental. They have to know you exist. They have to talk with you. And also important, they have to see previous examples of your work from you directly. Trust me, they will have questions and requests that only you can answer. A working relationship between you and the customer is one of the most important ingredients in this kind of business.
My recommendation is to forget the photographer middleman and do it yourself. I actually think it will be more work to market through someone else than to market yourself directly. In fact, I`m experimenting with marketing through a couple realtors. I`m pushing on it because the realtors are enthusiastic and people like my work, but I have yet to get a commission this way. All that I`ve been able to get so far, I`ve gotten myself.