I had a builder with only 1 build left. I sold the builder back using the little minus sign next to the skull. Click the skull and it will ask you if you would like to remove the "?" from the game. Each unit you sell will give you a different gold amount some are extremely large. You can use the policies cards I would image to really save some coinage and make some gold with the discounts if you really wanted to... Going back to my builder. I sold the builder for $162 gold. Produced the builder again in 4 turns with my first city. This makes the builder basically 1/2 price. I wonder how much gold you would get from one of the great persons? I usually play the trading/economy strategy in civVI so this is right up my alley.