A B C Plumbing & Heating Co.

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.

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.

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 Los Angeles Heating permits are required makes you appear to be a well informed customer.

The question is great for some industries and non-applicable for others. A general contractor, for example, will by definition employ subcontractors. Most Los Angeles Heating companies do not, but there are exceptions. You should always ask this question to your service providers. If they do use subcontractors, ask if they're all licensed and insured independently.