CGK Business Sales

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 District of Columbia, 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.

This really only matters if you have a preference, but it is good to ask. If you have a strong ideological belief about unions or nonunions, it's perfectly acceptable to make a decision based on the preference.

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 Washington as well, which will give you a broader view of customer satisfaction for a given company.

These first two questions should only relate to services or good purchased directly from the service provider. Many products carry their own warranties, like roofing shingles or siding. It's useful to know what these warranties cover as well as how long they last. The "warranty agent" question is important, because often warranty agents work with the manufacturer to get you repairs under warranty at a much lower price.