1 Corinthians 9:7

Who goeth a warfare any time at his own charges? who planteth a vineyard, and eateth not of the fruit thereof? or who feedeth a flock, and eateth not of the milk of the flock? (KJV)

Then: Paul continued explaining that everybody expected and deserved to be paid (receive food and sustenance from) for their work. Robertson and Plummer (under IX, 7) note the soldier worked for pay, the vine planter was a small business owner, and the shepherd worked as a slave. Congregational members at Corinth surely had more prestigious work, but would understand the principle.

Now: Members of church congregations expect and receive pay for their work. The principle is the same for ministers and staff. They deserve payment no matter their occupation.

Extra source: A Critical and Exegetical Commentary on the First Epistle of St. Paul to the Corinthians by Archibald Robertson and Alfred Plummer (Charles Scribner Sons, 1911) online at http://www.archive.org/stream/stpaulcommentary00robeuoft/stpaulcommentary00robeuoft_djvu.txt