Goats mature after 5 days, at which point they will produce Goat Milk every second morning. Once sufficient friendship and happiness is reached, they will produce Large Goat Milk. Goat Milk can be collected using a Milk Pail.
Goats can be sold. The selling price is dependent on how many hearts the animal has (data-sort-value="5200">5,200g max).
To sell a coop or barn animal, right-click the animal after petting. The friendship/mood interface appears. Move the cursor over the gold coin button at the right to see how much you can sell the animal for. Click that button and the confirmation that follows to complete the sale.