Let me say something dangerous. Almost every commentary ever written on the start of Luke 16 is wrong.
Whenever you hear anyone say that, automatically be suspicious! What makes me right and lots of very godly, very thoughtful commentators wrong? In this case (as in almost every case), that the meaning is completely dependent on context and structure and very many commentaries don't take account of either.
Let me explain. Start off by having a read of Luke 16:1-13. It seems as if Jesus is telling a story of someone who is dishonest but that the story implicitly commends the dishonest practice (v9: "And I tell you make friends for yourselves by means of mammon, so that when it fails they may receive you into eternal dwellings.") The way that many commentaries deal with this is to say that we shouldn't push parables too far, that they generally have only one point and that what is being commended here is shrewdness and being savvy to the ways of the world, rather than dishonesty.
I couldn't disagree more and its the context that gives it away.
Luke 15 and 16 go together. Jesus is eating with tax collectors and sinners. The religious establishment hates it and is, typically, muttering in the background. So Jesus tells a set of parables that are designed to expose their hearts. The most famous is that prodigal son in chapter 15. The point of the prodigal son is not, primarily, the return of the younger son, it is the refusal of the father's love by the older (ie the religious establishment).
The contrast in that parable is between one son who is utterly undeserving and is justified entirely by the father's grace and a second son who believes he has always been good enough for the father, scorns his love to others and refuses to accept it for himself. He seeks to justify himself.
Remember that as we come to the parable of the shrewd manager. Here is a story, told to the religious establishment, of someone dishonest, who misuses his boss's possessions but who so manipulates things that he gets justified in the eyes of others. Clearly this is meant to be another direct stroke at the Pharisees for the way they treat the things of God but seek to be justified by human activity. The clincher that shows that the shrewd manager is the self-justifying religious Pharisee is the way Jesus concludes in v14:
The Pharisees, who were lovers of money, heard all these things, and they ridiculed him. And he said to them "you are those who justify yourselves before men but God knows your hearts. For what is exalted among men is an abomination in the sight of God."
In other words the commendation of the rich man in the parable is not meant to show that the actions of the dishonest manager are commendable. It's meant to show the exact opposite. This is not a positive parable about something positive to emulate, it is a very negative parable about an abomination in the sight of God to be avoided at all costs.
But what is it that we are to avoid? Dishonesty? Clearly that's true, but it's not the thrust of the parable. What we are being told to avoid is the religiousity that justifies itself, manipulates situations to try to convince ourselves that our sin won't result in disqualification. The contrast is with the prodigal son. Here are religious people who justify themselves. The shrewd manager is the older brother. Both contrast with the prodigal (=those who Jesus was partying with), who, though sinful, was welcomed and restored entirely by God's grace.
Let's flee justifying ourselves, either by religion or by human shrewdness. Jesus sees right through both and isn't fooled. He justifies neither. Only those who receive it from him as a free gift.