In Cicero's "On Duties", he outlines for his son, Marcus, some principles to which man must adhere in order be moral. The essential conflict, according to Cicero, is not between "right" and "advantage," but between "right" and "apparent advantage" . The advantageous and the righteous are synonymous, and hence the truly a morals man, whom Cicero infers is hypothetical, will never have moral dilemmas since he will always recognize this sameness. He says that "it is sinful to even attempt a comparison between the two things, even to hesitate between them". Indeed, Cicero feels that "those who habitually weigh the right course against what they regard as advantageous  judge everything by profit and loss". Their ambiguity comes from selfishness
But for those people who genuinely have occasional struggles, the dilemmas are there because knowing what is right is not always clearly defined. Cicero gives some examples of this. For instance, is it morally acceptable for an important man to steal from an insignificant man if the former's subsistence is at stake? Should one depose a tyrant if that tyrant is his/her best friend? How much disclosure is a seller obligated to reveal about his/her product?
The one consistency in the answers to all these questions is the welfare of the greatest number of people. It is, for example, morally acceptable for the important man to steal if his intentions are not selfish but altruistic, that is he intends to use his skills to serve society. One's duty to one's friend is superseded by the greater evil of tyranny. And the seller must disclose all the defects of his product because without everyone's confidence in this kind of honesty, the market destabilizes.
Today's professionals would not reach the same conclusion as Cicero. If the binary is framed as expediency vs. obligation, the question has to be asked to whom one is obligated. Cicero mentions the gods, but many professionals today don't even believe in a higher authority, and if they do they don't necessarily know what the moral strictures of that authority entail.
As for the common good, this country was built on the principle that the majority would be served provided it didn't violate the innate rights of the minority. Cicero makes no such concession. He claims that violating what we have come to believe are a person's innate rights is justified if the larger society benefits. This is not to confuse the moral with the legal, but an American professional today must feel some resonance of our constitutional system.