Cari Mason checked "for sale by owner" ads on Craigslist thinking she could save money buying her son's first car.

But Mason said several "by owner" ads were really used car dealers pretending to sell personal vehicles that had clean histories.

"Every single one of them had damage on it. They were not truthful about anything," said Mason.

So, how common is that practice?

Action 9 responded to "by owner" ads with a hidden camera.

A Channel 9 producer called about a 2005 Honda Civic and talked to the seller.

"He was selling his own car?" Ulrich asked the producer.

"Yes," said the producer.

"Condition?" asked Ulrich.

"According to him, perfect," the producer said.

Action 9's research found the same guy advertised at least three other cars "by owner" that week. Later, when Ulrich stopped by, the man denied trying to sell us the Civic.

"Look, I don't want to talk to you. What are you talking about?" the man said to Ulrich.

"Why are you pretending you're not selling it?" Ulrich asked.

"That's not my car, it's my friend's car," the man said.

He said the Honda was at his friend's house.

"I'm going to take you to the car right now," the man told Ulrich.

But Action 9 never saw him again. Three hours later, Ulrich found the Honda he was trying to sell in the man's back yard.

Action 9 also called about a 2005 Acura sold "by owner," but the address turned out to be Rotec Motor Sales.

On hidden camera, the dealer told a Channel 9 producer it was his personal car.

"Was it really your car?" Ulrich asked after showing up at the dealership.

"No," the man said.

"Why did you list it on Craigslist that way," asked Ulrich.

"(I) don't know what you're talking about," he said.

Out of the five ads Action 9 responded to, three vehicles had accidents on Carfax reports or damage the sellers had not disclosed.

Florida regulators said dealers cannot hide their identity, and selling multiple cars each year without a license is illegal.

"It was a nightmare, actually," said Mason.

The Division of Motor Vehicles investigated 1,300 cases last year.

If you're buying from a dealer or from a private owner, have the vehicle inspected and check its history with Carfax.