He dropped out of high school in ninth grade. Got busted for carrying a load of cocaine. And dabbled in marijuana grow houses.

Angel Castillo Jr. finally found his criminal calling as an entrepreneur in South Florida's multibillion-dollar underground industry -- Medicare fraud.

''I started off driving a Ford Ranger and I ended up driving a Range Rover,'' said Castillo, 33, who is serving a 20-year prison sentence for defrauding millions from the government's healthcare program.

He is cooperating with the U.S. attorney's office and FBI to seek a reduction in his sentence, which is eight times longer than the average Medicare defendant's prison term.

Castillo, who grew up in a Cuban-American family in the Fontainebleau section of West Miami-Dade, controlled about a dozen medical equipment companies -- all incorporated in other people's names to hide his ownership interest so that federal authorities could not trace the businesses to him.

Castillo said he paid a premium for at least three of those companies because they came with recently arrived immigrants already registered as straw owners with Medicare.

Among them: Miami's Garcia Medical Supply Inc., which was headed in June 2006 by Anabel Esquivel, according to state corporation records. She entered the United States as an undocumented Cuban migrant four years earlier.

With Esquivel as Castillo's straw owner, Garcia Medical Supply submitted $3.6 million in false bills with Medicare between June and September 2006, according to federal claims records. Esquivel, who was living in a Hialeah Housing Authority apartment at the time, could not be reached for comment because she has returned to Cuba, according to tenants in her former unit. She has not been charged with any crime, and Garcia Medical is no longer active.

Another one of Castillo's businesses with a straw owner, Rodan Durable Medical Equipment Inc. in Hialeah, billed Medicare for $5.2 million in phony claims between August and November 2006, federal claims records show. Rodan is not in business now either.

EXTRA PROTECTION

Esquivel and other immigrants -- some of whom were smuggled into the United States, according to federal agents and immigration records -- provided extra protection to Medicare scammers from authorities, especially if they returned to Cuba after a short stay.

''I purchased three companies like that,'' Castillo said during a recent interview at the Federal Detention Center in downtown Miami. ``If you want the straws to go back to Cuba, you have to pay the sellers of the companies an extra $30,000.''

FBI agents and other federal authorities confirmed his story.

In total, Castillo was convicted of billing $48 million in false Medicare claims through eight of his medical equipment companies in 2005 and 2006 -- though the three businesses using Cuban migrants as straw owners were not cited in his plea deal, according to court records and federal authorities. His eight healthcare companies raked in about $8 million from the government health insurance program, according to court records. He personally pocketed more than $2 million.

Six other business associates were convicted with him on Medicare fraud charges.

Castillo admits he had no particular skills in the healthcare field. Then again, none were needed. After he served a couple of years in prison on a 1995 cocaine trafficking conviction in Georgia, Castillo learned a trade as an electrician. By the time his five-year probation was over, he was in the marijuana grow-house business.