The following except is quoted from George Muller's Autobiography, March 8th, 1843. The most impactful point of this excerpt is Muller's lifestyle. He did not take a salary from the church or orphan home he worked. He instead prayed daily for God to bring in the funds through donations. However, the point here is not salary but focus.
...When a believer is doing the work that God has called him to do, he may be confident of success in spite of obstacles. The first thing he has to ask himself is: Am I in a calling in which I can abide with God? If you cannot ask God's blessing upon your occupation, or if you would be ashamed to be found in it when the Lord Jesus returns, or if it hinders your spiritual progress, then you must give it up and be engaged in something else. But this is only necessary in a few cases. Most occupations are not of such a nature that a believer would need to give them up in order to maintain a good conscience before God, although certain alterations may need to be made in the manner of conducting the business. The Lord will direct us in this if we wait upon Him and expect to hear His voice.
The next point to be settled is this: Why do I carry on this business, or why am I engaged in this trade or profession? In most instances the answer would be, "I am engaged in my earthly calling so that I may support myself and my family." Here is the chief error that causes almost all the other errors by children of God concerning their calling. To be engaged in a business merely to obtain the necessities of life for ourselves and family is not scriptural. We should work because it is the Lord's will concerning us. "Let him labour, working with his hands the thing which is good, that he may have to give to him that needeth." (Ephesians 4:28)
The Lord generally meets our needs through our jobs. But that is not the reason why we should work. If providing the necessities of life depended on our ability to work, we could never have freedom from anxiety. We would always have to say to ourselves, "What will I do when I am too old to work, or if I am sick?" But if we are engaged in our earthly calling because it is the will of the Lord for us, He is sure to provide for us because we labor in obedience to Him.
Why do I carry on this business? Why am I engaged in this trade or profession? These questions should first be settled in the fear of God and according to His revealed will. We will then answer honestly, "I carry on my business as a servant of Jesus Christ. He has commanded me to work, and therefore, I work." Whether a believer chooses to become a missionary, a teacher, a carpenter, or a businessman, he will be blessed and find satisfaction in his career--as long as he works in joyful obedience to the Lord.