It depends on the home. If the home's features, amenities, or land characteristics are distinctive and unusual, the realtor and appraiser might have to use comparable sales from quite a distance away. A home that is in a suburban neighborhood most generally will be compared to like homes within just a few blocks.

Our home is in a rural area, so comps can be miles away.

Around here (central urban area of a medium sized city) it seems that recognized neighborhood boundaries play into it more than anything.....? Im a block over the river from an expensive gentrified area - still nice location, and close enough to the amenities, but prices distinctly lower (ie affordable enough for me to buy!)