What was Amos's occupation before the LORD called him to prophesy?

Answer: A herdsman

Amos told Amaziah he was not a prophet or a prophet's son but a herdsman and a tender of sycamore-fig trees.

““I was not a prophet,” Amos replied, “nor was I the son of a prophet; rather, I was a herdsman and a tender of sycamore-fig trees. But the LORD took me from following the flock and said to me, ‘Go, prophesy to My people Israel.’”— Amos 7:14-15 (BSB)