Not trusting anything or anyone certainly is no way to go through life. It is called "paranoia." That is why I like the idea of trusting that people will be as they are. Generally people will care first for their own paycheck, or at least for their own job. So a realtor who represents you will often (perhaps unconsciously) urge you to buy a more expensive house than you might need, because their commission is higher. And your trusted financial advisor will often advise you to buy and sell your assets because that's how she gets paid. There are exceptions, of course. I do know that the realtors and financial advisors who stay in business are often the ones who are as they are. They would rather take home a bigger check rather than a smaller one.
Are these bad people? Only if we expect them to have our self-interest first. They didn't get into these business so they could give money away. Our problem comes when we expect them to be our best friends. (As I say this, I feel gratitude for our fine realtor who brings us wonderful pies each Thanksgiving.)
I was surprised to hear a priest tell me that one of his biggest challenges is to attract a congregation. Here is a person committed to saving all beings (or some variation of that), and at the same time, focused on being fiscally responsible. A contradiction? Even zen temples have competition. May the best one win. (Did I hear something about "no gain?")
Milton Friedman insisted that we should eliminate the requirement that doctors are licensed. One of his reasons was to break up the monopoly of the AMA. But another was his belief that we don't pick doctors based on their license, but rather on their reputation. And if they don't perform well, there are the opportunity for civil suits. Will anyone hang out a shingle? Maybe. But will they have patients? We'll see. How is it that we trust our doctor (or not)?