CornerStone Mechanical

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.

This is very important, since an estimate is just that. Many contractors will submit a "paper estimate", meaning they've written the estimate down on paper. The bill is the true amount owed and will almost always say "Invoice" or "Bill" at the top of the page. The bill should also list the date it was issued, the due date of payment, and a list of services rendered.

You'll certainly want to ask them this. Steer clear of any company that is not insured in Colorado, 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.

You'll always want to ask how long the company has been in business in Denver. While this isn't a guarantee that the company will do good work, companies with longevity on their side must be doing something right. That being said, there are newer companies that do great work. If the company is under three years old, ask where the owner was employed before and for how long. If he/she has a long history of employment, it's reasonable to infer that he or she decided to go into business for themselves after so many years of experience.

Though a standard question, it's important to ask. Most contractors will tell you how long they expect the job to take without you asking. If they don't volunteer that information, be sure to ask. It's also helpful to ask if that's a hard finish date, meaning that it's the definite finish date. If it's a soft finish date, it may be extended for any number of reasons.