"So also the Lord directed those who proclaim the gospel to get their living from the gospel" (1 Cor. 9:14).
This verse, along with the verses leading up to it, shows us God's design that those who devote their lives to preaching the gospel ought to be able to make a living from their work. Local churches and individual Christians ought to take this seriously. Are they, to the best of their ability, allowing those who labor in the gospel to devote their lives wholly to that work?
When we consider the responsibility to "support such men" (3 Jn. 8), we need to properly understand the nature of that support. It seems there are some who view the money they give to a preacher, at least to some degree, as benevolence. They are helping someone who is in need. The reason he is in need is because he has devoted his life to preaching instead of getting a job that will allow him to support himself and his family. This is not how the New Testament describes a preacher's support.
Paul told the Corinthians, "I robbed other churches by taking wages from them to serve you" (2 Cor. 11:8). The money Paul received for preaching was not benevolent aid. He was paid wages. Wages are that which you earn for what you do. Therefore, when deciding what to pay a man for his work in preaching, it is right to pay him based on his work, not his need.
A word to preachers: There may be times when brethren will not or cannot provide enough support for you to completely devote yourself to preaching. In those cases, do what Paul did. Work while you preach (Acts 18:3-4; 20:34). It may not be ideal, but it can be done.
Preachers need to preach the gospel. Brethren and local churches ought to do what they can to allow those who preach to make their living from the gospel. Let us all take our responsibility seriously.