"Maria Branca dos Santos, or more commonly called "Dona" Branca, was a poor Portuguese woman when she decided that she would open her own "bank" in 1970. To make it attractive, she promised an interest rate of 10% per month, and got thousands of clients (including the working poor of Portugal) to give her their money.
The scheme lasted more than 14 years, and during this time she's known as "The people's banker." Dona Branca was arrested and sentenced to 10 years in prison. She died poor, blind, and alone.
In 1993, her crime inspired a Portuguese soap opera titled A Banqueira do Povo ("The People's Banker")."
Source: Neatorama