I have found in my experience that homeowners will rely on the minimal to know what to list their house for, sometimes going off a home in their neighborhood. I think it essential to inform homeowners in detail about the work that goes into listing a house.
I want to just touch only on a few points and encourage you to reach out to any agent you may know (or maybe a new one, hint, hint, wink, wink)
Information needed and researched would be Tax Records, history from the MLS (past sales), input from the homeowner on additions, upgrades, etc. We then pull properties within a radius and widdle it down to the most similar features to the home in question.
This is just some of what we do as your agent to give you a range of the best price to list your home at.
Of course, there are other benefits of having an agent list your house, that's for another day.
I think it is important to note the difference between a CMA and an Appraisal. A CMA (Comparative Market Analysis) is an in-depth report on a house's value now, and appraisal is done by a licensed appraiser on behalf of a financial institution.