I would recommend you look for a flat-fee. Although not always true, people who charge on an hourly-basis may charge you down to minutes and seconds. Perhaps you call them during the build process to ask a simple question. If they charge on an hourly-basis, that 5 minute phone call may have just cost you extra money.
For example, we charge a flat-flee for the project as a whole. All of our pre-contract discussions or consultations are always free. After I have met with a potential new client I will send them a detailed email outlining what I believe their needs are and what type of website will suit them best. I will also provide them with a cost estimate of the project. My cost estimates are based on how long I think the project will take to complete. If I project that their website will take 30 hours to complete, their billing will stop at 30 hours. If the project takes longer than 30 hours, my clients are not charged for the extra time.