> your risk in buying a business goes down if the current owner under-appreciates what they have
This is completely true, my sentiment is more for the idea of a "turn-key business" acting like an annuity. I don't think every business for sale is going down but I think there's a large enough risk case that I'd rather avoid it.
Perhaps I'm naive, but I think your risk in buying a business goes down if the current owner under-appreciates what they have, and you have the skills to do it better than them.