Reading Crown Court heard 37-year-old Thatcham father-of-two Justin Tidbury was involved in 'dodgy dealing' between November 2003 and May last year.
On one occasion he sold a 55,000-mile Renault Laguna after knocking 32,000 off the odometer, and when advertising cars on the Auto Trader website he falsely claimed they had a full service history.
He then began acting as a finance broker despite being refused an essential credit licence by the Office of Fair Trading.
The OFT ruled he was not ‘trust-worthy and reliable’ even without revealing a criminal record containing 74 previous offences, including tampering with mileages, theft and drink driving.
He was trapped when West Berkshire Council trading standards department began investigating a customer's complaint.
Tidbury, whose address was given as Yeomanry House, Thatcham, operated under different names including Abbey Motor Company, and had showrooms in Newtown Road and at Monks Lane Service Station, Newbury, the court heard.
Jonathan Whitfield, defending, said: “Tidbury was someone behaving illegally, but also behaving stupidly. He didn't take the system seriously. He now does so."
Judge Mary-Jane Mowat said: "I take the view that you were completely cavalier and contemptuous of the law that is there to protect customers."
She added: "There is a thread of dishonesty running through the whole way that you ran this business until you were discovered.
"You have a record of offending. I regret the effect of this on your employees and those who depend on you, but this is so serious that a custodial sentence is inevitable."
Tidbury admitted giving false or misleading information, illegally running a credit business and giving false trade descriptions.
An application was made under the Proceeds of Crime Act to confiscate the proceeds from Tidbury's activities.