Can you expound on what you mean by "usually at the expense of people poorer than them"? I understand this sentiment when it comes to things like predatory lend

Can you expound on what you mean by "usually at the expense of people poorer than them"? I understand this sentiment when it comes to things like predatory lending, but would like to learn more about how it applies to non-exploitative areas. A couple possible examples to help with the discussion: 1. A new millionaire buys a house from someone in SF and lives there. 2. A new millionaire buys a rental property from someone in SF, renovates it, and raises the rent to make back their capital outlay. 3. A new millionaire buys a broken down classic car, invests capital into repairing it, and sells it to a collector for a profit.