In 1 Kings 19:19-21, we read of Elijah calling Elisha. Elisha was working hard in the fields with his oxen when Elijah called him.
Notice first of all that God always calls those who are working hard and are faithful in their secular occupations. Moses was faithfully looking after his father-in-law's sheep when God called him. David was looking after sheep and fighting with lions and bears. Amos was a hardworking herdsman. Peter, James, John and Andrew were hardworking fishermen. Matthew was sitting at the table working on his accounts. We never see anywhere in the Old Testament or the New Testament that God called a lazy man for His service.
We don't find Elijah going to Elisha's house when he was fast asleep and calling him there - because we would have thought he was a lazy man. Jesus also never went to Peter's house in the evening to call him. He called him when he was fishing. All these examples show us that God wants us to be faithful and hardworking in our secular jobs before He can call us to serve Him. If you are not faithful in earthly matters, how can you be faithful in heavenly matters? If you are young and still living at home, then be a faithful son or daughter at home.
Notice secondly that all these men dropped everything and went as soon as God called them. We see that with Peter, John and Matthew and also here with Elisha. God calls those who will respond to His call immediately and wholeheartedly. They may seek to confirm God's call on their lives with godly people in order to be certain that they are not acting on their own emotional feelings. But once they are sure, they act quickly. God can use only such people to serve Him, because His service requires instant obedience, total commitment and hard work.
God tests us in our secular occupations to see whether we are faithful. If you are asked to clean a room and you are careless about the way you do it or you are slipshod about it, I doubt if God will ever call you to serve Him. Because, if that's the way you clean up a room that will probably be the way you clean up your heart as well. How then can God use you to clean up His church? It is faithfulness in the little things that God looks for.