It's rare when people don't know they have something of value. The reverse is probably more true. People think they own something they saw on TV and that it's going to be valuable. It really depends on where the appraiser is located. Obviously you're going to make more in Atlanta than in Valdosta.
Some appraisers get paid per item or per hour, it depends on the amount of time involved.
It depends on how much time you actually bill. I still have an interest in seeing what I haven't. My curiosity is there. I never know what I am going to see when I walk into a house. There's an unbelievable variety and quantity of goods that have been made over the centuries.