Many people hire contractors for home improvement projects during the summer, but not all the contractors bidding on projects have licenses, meaning they are breaking the law, reports James Taylor of CBS News Sacramento.

In California, there have been many undercover stings trying to find these unlicensed contractors. According to Katherine White of the Contractors State License Board, one sting in July led to 11 people being caught.

“If you are asking for a bid over $500, you need to have a valid contractor’s license,” White said.

It’s a law designed to make sure those doing the work have the proper skills and protect the customer.

“That’s the key reason why you want to hire a licensed contractor,” White said. “You know the quality of the work is going to be higher than that of an unlicensed contractor.”

It also helps avoid excessive down payments.

“Any contractor should be asking no more than $1,000 or 10 percent of the total contracting price, whichever is less,” White said.

Illegal contractors often target victims of disasters, like fires and floods.

“They know that someone wants to rebuild fast and so they’re out there, and they’re often asking for the entire price of the job upfront,” White said. “And it’s also a felony to be contracting without a license in a declared disaster area.”

So how can people hire a reputable contractor? One builder has some advice.

“Local supply houses know the good and bad contractors and they will not give you a bad referral, so get a few names from them and that’s how you pick your contractor,” said Derek Sherrell, a developer.

California also maintains a public database where people can check to see if someone is licensed and even search for contractors in their neighborhood.

“You really want to make sure you’re properly vetting them to make sure you’re getting the best person for the job,” White said.

Unlicensed contractors face fines of up to $1,000 for a first-time offense and repeat offenders could be sentenced to jail time.