Looking through the window and mail slot on the door, the agents noted that there was no equipment inside the building, just a group of stacked boxes and some mail on the floor.
But the company still managed to bill Medicare $158,000 in the month of March, according to the FBI.
At another address, agents found an empty office space not much bigger than a typical walk-in closet. The FBI said that company billed $400,000 in March, and more than $1.1 million total.
Waterman pointed out that the company purported to sell durable medical goods, but the office wasn't big enough to store any of the wheelchairs, ventilators or other supplies a legitimate business would have on hand.
"I think you'll find it's easy," special agent in charge Christopher Dennis said of the alleged fraud schemes, "because Medicare is set up on rules and regulations that were set up decades ago. We're trying to govern, detect and prevent fraud with a system that was established many years ago, in 2009."
Dennis works out of the Department of Health and Human Services' internal watchdog body, the Office of the Inspector General. That office has released numerous reports documenting suspected health care fraud in south Florida.
Medicare "was originally set up on the honor system," Dennis said. "And, of course, here in south Florida, we're finding that the perpetrators are not all that honest."
One phony company prosecuted in south Florida got the Medicare ID numbers of 200 people and billed the government 200 times for the use of the same motorized wheelchair -- at a cost of $1 million.
"They're called wheelchair parties," said Alex Acosta, the U.S. attorney for the southern district of Florida. And with some of the chairs costing up to $20,000, he said there's money to be made.
"It's the same wheelchair over and over… a million dollar wheelchair. It's billed again and again and again, never given to a patient," Acosta explained. "The patients don't need it. It's all fraud."
Acosta showed ABC News the wheelchair used as evidence in the case. It's stored in a warehouse, along with the boxes and boxes of case files for that and other health care fraud cases.
In some cases, even patients are part of the scam. One undercover video provided by the FBI shows a staff member at an HIV clinic paying a patient a $250 bribe to keep quiet.
The clinic then billed Medicare $12,000 for services never rendered, one of many fraudulent claims totaling more than $2 million. Federal prosecutors won convictions against the owners of that clinic and a physician who worked there.
"The level of Medicare fraud down here is utterly disgusting," said Acosta.
"It is an epidemic down here, but I think it's important, too, to say, it's not just in south Florida," he added. "It is across the nation, and it is disgusting and it really needs to stop."
But as long as criminals believe these types of scams are easy, they're unlikely to stop, the FBI informant said.
"It is too easy to steal from the government ... it's too easy to steal the money, and everyone is just going for the easy money," he said.
Your money, stolen by the millions, every day.