"Don't you know that those who work in the temple get their food from the temple, and 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." NIV translation
Paul says again that the biblical pattern is for God's servants to be taken care of by God through the offerings at the temple.
"But I have not used any of these rights. And I am not writing this in the hope that you will do such things for me. I would rather die than have anyone deprive me of this boast. Yet when I preach the gospel, I cannot boast, for I am compelled to preach. Woe to me if I do not preach the gospel!" NIV translation
We see Paul's heart in the fact that he does not preach for personal gain but because of what Jesus Christ did for him. He could brag about how he did not take money from the church for his ministry but he does not because he realizes that it is a minor thing compared to what Christ has done. He could not have done anything else but preach the gospel. There are many today who view preaching the gospel as a career instead of a calling. Those that hold that view are the ones that will be in it for the earthly rewards and it will be obvious.
"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." NIV translation
Paul's greatest joy was to be able to freely preach the gospel. He did not charge a speaking fee or sell books and tapes but instead freely gave what he was given by Jesus Christ. He did not have to take up a "love offering" or worry about stepping on people's toes as he often worked to support himself.
"Though I am free and belong to no man, I make myself a slave to everyone, to win as many as possible." NIV translation
Paul demonstrates his humility in the fact that he does not demand his rights as an apostle but instead serves all men. The "make myself a slave" is not simply talking about serving but instead is speaking of an attitude. Paul considered everyone else to be better than himself (that is the attitude of a slave). The purpose of this attitude was to win others to Christ and that should be our purpose in life as well.