I don't get hired to re-inspect chimney repairs often, but when I do, I'm often disgusted. Here's how it works: the home inspector says the chimney needs repair, and the buyer tells the seller to fix the chimney. The sellers usually hire the cheapest chimney repair contractor they can find... and it's usually an unqualified hack with a trowel.
Just as there is a big difference in the quality of work between home inspectors, there is a similar gap in the quality of work between good chimney contractors and hacks. I'd like to share a couple of our recent encounters with these chimney hacks.
The $214 Chimney Re-Build
I inspected a home in Saint Louis Park that had a chimney with bricks that were disintegrating, and in need of major repair.

Here's what I wrote in my inspection report:
The buyer went back to the seller asking for the chimney to be repaired, and the seller hired someone to fix it... for $214. That's a fraction of what I was guessing it would cost, so when the buyer learned what the seller paid for the repairs, he was rightfully suspicious and hired me to go back out. The photo below shows what I found:

I know what you're thinking - either "that's the same picture" or "where's the duct tape?", right? If you click on either of the photos for a larger view, you'll notice that in the second photo, someone simply slapped some mortar on the chimney; they didn't fix it. This chimney still needs repair.
The Disintegrating Chimney Crown
I inspected a home in Minneapolis with a chimney that had recently been rebuilt. The chimney walls looked great... but the crown was literally falling apart, due to a poor mix of concrete.