One Translation: "Presbyters who preside well deserve double honor, especially those who toil in preaching and teaching" (NAB).
Gordon Fee offers the following comments:
"It is clear from verse 18 that honor (see on v. 3) here includes at least pay. But it is highly unlikely that double honor means 'double pay' (as GNB), implying either twice as much as others who do not teach or twice as much as the widows. Rather it means 'twofold honor,' the honor and respect due those in such positions as well as remuneration" (1 and 2 Timothy, Titus, pp. 128-129).
From William Mounce's Word Commentary:
Paul begins the first of his four statements about elders on the same note with which he began and ended the preceding discussion of widows— honor— and in both cases honor involves money. The elders who were following his instructions and doing a good job not only were worthy of the peoples’ respect but should also be paid for their work (“double honor”). He will continue in v 18 with his reason: workers should be paid. This was Paul’s general rule (1 Cor 9: 4–6; cf. Rom 13:7) although he himself often chose to earn his own living (cf. 1 Cor 4: 12; 2 Cor 11: 7– 9; 1 Thess 2: 9; cf. 2 Thess 3: 7– 9; Acts 18:3).
Pastoral Epistles, Volume 46 (Word Biblical Commentary) (Kindle Locations 14412-14413). Zondervan. Kindle Edition.
Pastoral Epistles, Volume 46 (Word Biblical Commentary) (Kindle Locations 14409-14412). Zondervan. Kindle Edition.