Barzillai was a very old man, 80 years old. He had given the king food and other things when David was staying at Mahanaim. Barzillai could do this because he was a very rich man.
There was a very rich man living in Maon. He had 3000 sheep and 1000 goats. That man was in Carmel taking care of some business. He went there to cut the wool from his sheep.
Menahem raised the money by making all the rich and powerful men pay taxes. He taxed each man 20 ounces of silver and gave the money to the king of Assyria. So the king of Assyria left and did not stay there in Israel.