But that didn't last, either. In 2001, his best friend introduced him to the exploding Medicare fraud economy in Miami-Dade.

''A lot of people who used to be in drugs are getting into this business,'' Castillo said. ``You see it as white collar. There's not a lot of risk.''

Castillo got his foot in the door as a ''check-changer'' for operators of medical equipment companies that were filing false claims with Medicare and receiving hundreds of thousands of dollars in payments.

Castillo's role was to cash checks for less than $10,000 on Medicare accounts at local banks so the real owners could avoid financial reporting requirements to the Treasury Department. His take: 5 percent of each bank transaction.

Soon, Castillo was selling his name as a straw owner for medical equipment suppliers.

But the real money was in controlling the Medicare-approved companies -- a lesson he learned from an acquaintance now under investigation with alleged ties to a massive ring allegedly run by Mabel and Abner Diaz, of Miami Lakes. The former owners of All-Med Billing Corp. pleaded guilty earlier this summer to charges of submitting about $420 million in false Medicare claims for 85 medical equipment suppliers in Miami-Dade. Medicare ended up paying out $148.5 million on those bills. The Diazes' take: a 5 percent commission -- or about $7.5 million.

Castillo said he tapped into a network of relatives, friends and others from his pot-growing days to use as straws for his medical equipment businesses.

ON HIS OWN

''I went out on my own because I wanted to get the same amount of money as everyone else,'' Castillo said, explaining that ``only Cubans were involved. We try to keep it among us.''

To fool the Centers for Medicare and Medicaid Services, Castillo bought elderly patient lists and misappropriated physicians' ID numbers to bill the health insurance program for mattresses, knee braces and artificial limbs, among other items. CMS manages Medicare as part of the U.S. Department of Health and Human Services.

If elderly patients complained to Medicare about a bill for something, Castillo said he would bribe them to shut them up.

The goal was to churn claims as fast as possible without being detected. He said local Medicare billing companies -- such as All-Med -- became the ''eyes and ears'' for the equipment providers because they knew which supplies and codes would be approved by Medicare's private claims contractors.

BANK TELLERS

So much money was pouring in that Castillo bribed bank tellers to let his associates pick up bags of cash totaling as much as $100,000 from Bank of America, Union Planters and Washington Mutual, court records show. One teller in the scheme, Michelle Torres, was charged with money laundering and fled to the Dominican Republic, according to the FBI.

Asked if it bothered him that he was stealing from the U.S. government, he said: ``You want money for yourself -- it's greed. You don't see it as wrong. You see it as white collar. There's not a lot of risk. You don't live in fear because you don't think you'll ever get caught.''

For a few years, Medicare made Castillo a millionaire.

He rented an upscale South Beach apartment at the Portofino Tower, met his future wife at the Clevelander Hotel and ate all his meals at restaurants like China Grill, Houston's and Benihana. He bought $50,000 diamond necklaces, a Rolex and other expensive jewelry off shopping networks on cable television.

In December 2005, he said he put down $200,000 in cash to buy a four-bedroom, three-bath home for $570,000 in Cutler Bay.

''It changed my lifestyle 180 degrees,'' he said.

Castillo's life as a high-roller crashed last year. Two of his associates, Angel Hernandez Quesada and Juan A. Zaragoza, while under indictment, snitched on him. And it was only a matter of months before Castillo cut a plea deal.

But now -- separated from his wife and their 6-year-old son by prison bars -- Castillo regrets his career choice.

''If I knew I would have gotten 20 years, I wouldn't have done it,'' Castillo said. ``It's not a joke. We're taking money from the government that's for our seniors. Me and a lot of other people did the wrong thing with our money.''