There are two possible views of why Jesus prohibited the apostles from acquiring money:
This is not about refusing to accept payment (Matthew 10:8), but relates to Matthew 10:10,which refers grammatically speaking, to the verb acquire
in Matthew 10:9, in which the apostles are prohibited from gathering financial means prior to their journey, but must trust God alone for their needs.
An apostle had no need for or way to accumulate wealth, but had to dedicate himself wholly to his task. As such there is no contrast between Matthew 10:8b and Matthew 10:10. The labourer has the right to his wages, yet the apostles ought to be willing to labour, at least for now, without them. God will ensure that their basic needs are met so that they could fulfill their calling.
Interpretation 1:
The reference to acquiring no gold or silver or copper (Matthew 10:9) should not be understood in conjunction with the prohibition on the apostles in terms of accepting payment for their ministry Matthew 10:8), but rather with the next verse (Matthew 10:10), which is grammatically dependent upon the verb acquire
in Matthew 10:9, in which the apostles are prohibited from gathering financial means prior to their journey. The disciples can only take along the greatest necessities as they ought not to trust not in their material possessions, but on God alone for provision.
Interpretation 2:
Once one had been called to become an apostle, there would be no room for a career, as they would have to dedicate themselves wholly to their exceptional task. As such there is no contrast between Matthew 10:8b and Matthew 10:10. The labourer has the right to his wages, yet the apostles ought to be willing to labour, at least for now, without them. God will ensure that their basic needs are met so as to enable them to fulfill their calling1
9 Acquire no gold or silver or copper for your belts,