1 Corinthians 9:17

For if I do this thing willingly, I have a reward: but if against my will, a dispensation of the gospel is committed unto me (KJV)

Then: Paul has spent so much time giving the reasons for deserving pay, he needs to fully explain his reasons not to take it. Corinthians need to know that his willing attitude to serve freely is in itself a reward from God. Baker (p. 127) explains that the Greek uses one single word to mean "willingly" and another single word to be its antonym. Henry's comments give readers the word "stewardship" as a way to think about "dispensation." Paul's task is to dispense the gospel in accordance with the trust given him by Christ.

Now: Paul's example of serving for free has to be a point of consideration for all believers. Conditions and circumstances vary. What each needs is his/her own conversation and calling. The contract between God and the worker comes individually and should not be an argumentative point for those outside the contract. Only God can judge his servants.

Extra source: Cornerstone Biblical Commentary 1Corinthians (William Baker), 2 Corinthians (Ralph Martin & Carl Toney), ed. by Philip Comfort. Carol Stream: Tyndale House Publishers, c2006.Commentary on the Whole Bible Acts to Revelation Vol VI by Matthew Henry online at http://www.ccel.org/ccel/henry/mhc6.iCor.x.html