All Clean Duct Cleaning

This will be answered when you ask if all employees are licensed. The only way to obtain a legitimate tradesman's license is to be a legal or naturalized citizen of the US. The company may employ people in positions that don't require a license, however, so it's wise to inquire.

Many jobs in California will require municipal permits in order to be approved by the town's inspector. It's always good to ask who will be responsible for pulling those permits, and if you'll be expected to do it. You'll almost never be told to pull your own, but knowing that Sun Valley Cleaning permits are required makes you appear to be a well informed customer.

You'll certainly want to ask them this. Steer clear of any company that is not insured in California, because that means that any incidental damage they may do on your property will be a real hassle to recover compensation for. It is never wise to work with uninsured tradesmen of any kind. Most states also require that someone have insurance in order to be issued a trade license. If they say they're licensed but not insured, they're being less than truthful.

Always ask for references, and always check them. Keep in mind though that the only references you'll get are people who the contractor is certain will give him a good review. You'd also be well advised to check online review sources in Sun Valley as well, which will give you a broader view of customer satisfaction for a given company.