Does the Rosenthal Act apply to me if I lent money privately?

The Rosenthal Act has a genuinely broad reach and this is where people over-apply it. It captures original creditors chasing their own debts, not merely collection agencies, which is far wider than the federal position and catches many California businesses by surprise. But the definition has a threshold built into it: it reaches a person who collects debts as a regular part of carrying on a business. Someone who lent a friend money once, and is now trying to get it back, is not carrying on a business and is not doing this regularly. On the ordinary facts of a private loan, the Act does not describe you.

That threshold moves with your circumstances rather than your intentions, so it is worth checking honestly. Someone renting out property and chasing arrears, or advancing money to people repeatedly, may well be collecting in the ordinary course of business, in which case the restrictions on contact frequency, timing, involving third parties and misrepresenting consequences apply, along with a separate criminal provision covering documents dressed up to resemble court papers. And even where nothing in that Act touches you, conduct still matters. Threats, showing up at a workplace or pressuring someone through their family create exposure of other kinds and, more practically, they hand the other side something sympathetic to describe to a judge.