Malachi chapter 3 verse 3 -4
3. He will sit as a refiner and purifier of silver; he will purify the Levites and refine them like gold and silver. Then the Lord will have men who will bring offerings in righteousness, 4. and the offerings of Judah and Jerusalem will be acceptable to the Lord, as in days gone by, as in former years.
Malachi chapter 3 verses 10 - 12
10.Bring the whole tithe into the storehouse, that there may be food in my house. Test me in this,” says the LordAlmighty, “and see if I will not throw open the floodgates of heaven and pour out so much blessing that there will not be room enough to store it. 11.I will prevent pests from devouring your crops, and the vines in your fields will not drop their fruit before it is ripe,” says the LordAlmighty. 12.“Then all the nations will call you blessed, for yours will be a delightful land,” says the LordAlmighty.
1 Conrinthians Chapter 9 verses 2 - 5 (here paul speaks of his rights as a man of God)
2.Even though I may not be an apostle to others, surely I am to you! For you are the seal of my apostleship in the Lord.
3.This is my defense to those who sit in judgment on me. 4.Don’t we have the right to food and drink? 5.Don’t we have the right to take a believing wife along with us, as do the other apostles and the Lord’s brothers and Cephas
1 Corinthians chapter 9 verse 7
7.Who serves as a soldier at his own expense? Who plants a vineyard and does not eat its grapes? Who tends a flock and does not drink the milk?
1 Corinthians chapter 9 verses 11 - 14
11.If we have sown spiritual seed among you, is it too much if we reap a material harvest from you? 12.If others have this right of support from you, shouldn’t we have it all the more?
But we did not use this right. On the contrary, we put up with anything rather than hinder the gospel of Christ.
13.Don’t you know that those who serve in the temple get their food from the temple, and that those who serve at the altar share in what is offered on the altar? 14.In the same way, the Lord has commanded that those who preach the gospel should receive their living from the gospel.
my take is that offerings must be brought to the house of God in righteousness as stated in malachi chapter 3. You guys should also read 1 corinthians chapter 9, the whole chapter, and i have extracted bits of it up there for you to read. However, Paul also says in verse 18 that he preaches the gospel for free and does not make full use of his rights in verses 11 and 12 above as a preacher of the gospel. Others may choose to do so.
Some preachers choose to preach voluntarily and others are just discharging the mandate given to them i.e. a job! And they have a right to get paid by that job