If I preach voluntarily, I have a reward; if not voluntarily, I am simply discharging the trust committed to me.  What then is my reward? Just this: that in preaching the gospel I may offer it free of charge, and so not make full use of my rights as a preacher of the gospel. 1 Corinthians 9:17-18

            The apostle Paul worked for free, holding down a job and at times raising support for special missionary trips.  Working as a pastor for free has its benefits.  However, not every pastor has the time or talent to do so much.  Previously to this passage, Paul made a plea for pastors to receive payment for their work.

Don’t you know that those who serve in the temple get their food from the temple, and that those who serve at the altar share in what is offered on the altar? In the same way, the Lord has commanded that those who preach the gospel should receive their living from the gospel. 1 Corinthians 9:13-14