After much discussion, my husband and I decided against offering a up a room in our hypothetical house to our friends. While the extra money is extremely appealing, the extra stress is not.
We grew out of having a roommate a long time ago, and anything other than a short-term arrangement is just not reasonable. We're not having kids because we love our privacy, our intimacy, our marriage. Adding a person in there competing constantly for space, attention, resources, affection even.... it's just not okay.
So for now the house is on hold. We're going to remain hopeful that I find a new job before this house is off the market, but until we can afford this house without any other help, we simply can't move. It kind of breaks my heart, but I know we're making the right decision.