The cautionary tale begins with the president of the investment firm, who is behind bars after lying to investors and stealing nearly $8 million from his investors.

Postal inspectors say dozens were duped by an investment firm that tricked them into believing they were funding development projects.

"He took the clients that he built up over 25 years and started selling fictitious loans and overselling loans," Amy Kerkoff, a US Postal Inspector, said.

Instead, the president of the firm - who was not named in the report - used the money to pay off other investors whose money he had already stolen: A typical Ponzi scheme.

"He had a fleet of cars for his business. He spent a month in Hawaii with 20 family and friends and footed the bill for that, and he sponsored hydroplane races," Kerkoff said.

Postal inspectors say some victims were left with nothing.

"Ultimately, they have lost everything --they've lost their life savings and retirement. Many of them are older and will have a hard time recovering those funds," Kerkoff said.

Inspectors say there were red flags, like important paperwork was never received.

"They get too comfortable and didn't follow up. Do your homework and make sure you get everything linked to your investment," Kerkoff said.

Often, one of the first signs of a ponzi scheme is the promise of unusually high returns. And keep in mind, con artists can fake the paperwork. Research is key. Check out the actual investment to make sure it's real.