There are all sorts of lucrative pursuits that may not land you in jail, but that most of us would consider unethical. As one example, spamming. Another one,

There are all sorts of lucrative pursuits that may not land you in jail, but that most of us would consider unethical. As one example, spamming. Another one, black hat SEO. If you're careful doing these things, you can avoid breaking the law in many countries. Often, even in those countries where these pursuits are against the law, you'd never be prosecuted. So faced with these opportunities, there are many "psychopaths", "sociopaths", or -- to avoid pseudo-psychological terms -- unethical/immoral people who would not feel the hesitation you and I would feel faced with such possibilities. There are all sorts of borderline/"grey" opportunities like this available to immoral people. They are unlikely to land them in jail, but they don't hesitate so they make bank.