2 Cor. 11:7-12 (ESV)
Or did I commit a sin in humbling myself so that you might be exalted, because I preached God's gospel to you free of charge?  I robbed other churches by accepting support from them in order to serve you.  And when I was with you and was in need, I did not burden anyone, for the brothers who came from Macedonia supplied my need. So I refrained and will refrain from burdening you in any way.  As the truth of Christ is in me, this boasting of mine will not be silenced in the regions of Achaia.  And why? Because I do not love you? God knows I do!
 And what I do I will continue to do, in order to undermine the claim of those who would like to claim that in their boasted mission they work on the same terms as we do.
This is an amazing little passage. It seems the Corinthians actually wanted to pay Paul and were offended that He did not accept his support. Rather Paul says he robbed other churches by accepting their support, rather than the support of the Corinthians. The question is why? Partly to emphasize that the Gospel is free. Paul very easily could have accepted support from the Corinthians. The Corinthians were accustomed to paying people to teach them different religious and philosophical things. But Paul wanted to distinguish himself from the others and what they taught. So at least at first he refused payment from them. (Interestingly, it seems he didn’t actually pay for his own way with his “Tent Making Ministry.” He at least received some support from other churches.) This should still be the model on the mission field. Missionaries should receive their support from other churches, at least at the beginning. At some point though, the new churches they begin will want to support themselves and their pastor, perhaps they will even want to support another church, and the missionary there.