What is the biblical basis for requiring that a pastor/preacher/teacher/etc be paid for their ministry? What is the biblical basis for requiring a minister to be paid for their work?

Put another way, what is the biblical basis for supporting the notion of a solely-vocational pastor?



Note - I am NOT looking for a biblical basis that paying a minister anything  is OK: there are myriad passages that could be turned to for that. This is exclusively about a mandate for such recompense.
In 1 Cor. 9:14, the apostle Paul wrote, 


  Likewise, the Lord ordered that those who preach the Gospel should make their living from the Gospel.
  
  οὕτως καὶ ὁ κύριος διέταξεν τοῖς τὸ εὐαγγέλιον καταγγέλλουσιν ἐκ τοῦ εὐαγγελίου ζῆν (TR, 1550)


In his commentary on 1 Cor. 9:4, John Gill wrote,


  "Even so hath the Lord ordained"
  
  That is, the Lord Jesus Christ (in Matt. 10:10; Luke 10:7-8), it is an order and appointment of his that his ministering servants, who labour in preaching his Gospel, should be sufficiently taken care of, as to a comfortable livelihood; he has not indeed fixed it in the same way as the priests and Levites had theirs under the law; but as the one was just and right, that they should be maintained out of the things belonging to the temple and altar, and live on them, so it is his will and pleasure,
  
  "that they which preach the Gospel;"
  
  that continue to do so, that labour, and not loiter in the word and doctrine, who do the work of the ministry fully and faithfully, and not bear the name only of Gospel preachers: should live of the Gospel; not the Gospel itself, which is spiritual, and not corporeal food; but the sense is, that in consideration and because of their preaching the Gospel, they should be supplied with the proper necessaries of life:


I bolded what is of utmost importance. I preach the Gospel, but I do not do so "fully." It is not my sole occupation. I am not fully committed to doing so. But those who are, whose sole purpose is to preach the Gospel, they should be fully supported. Else, how shall they devote themselves to fully laboring in the word?

The apostle even confessed that he had the authority to forbear working (1 Cor. 9:6). Would Christianity have grown and thrived the way it did without the apostle Paul devoting his entire self to preaching the Gospel?