There are almost as many flavors of estimates as there are contractors.  One of the most important exercises you will do while selecting a contractor is comparing bids.  Oftentimes, this is difficult because various contractors will organize their estimates in different ways.  Take the time to try and align apples to apples.  Ask as many questions as you need to understand what has been included in numbers.  It is relatively easy for contractors to “get their foot in the door” with a lower number.  They accomplish this by excluding items that will need to be done and by including unrealistic allowances.  Understanding the quality level assumed in any allowances is critical.  Be sure you understand what has been priced and that it matches your expectations.  Ask about change orders:  are they likely, what would be an example of one, how often do they occur on your projects?