All design and development work, including website maintenance, is billed per hour and prepaid. Block of hours are prepaid before the work is started, and the hours never expire. If we've designed your website, you'll get a discount on any hourly maintenance, and the discount never expires.
Before we start you'll be given a rough estimate of how long a given task or project can be expected to take, how many billable hours are involved, and how much it will cost. For projects taking more than a few hours a written proposal is sent, and that quote/time estimate is good for 24 hours, because my schedule changes and fills up quickly. You'll be given access to our online time report, where all time worked is logged and updated in real time.
My estimates are normally very accurate. I've been in business for 15 years, and the time taken for each and every project I've done, large and small, has been recorded and analyzed, and compared to other similar projects I've done. I use an online timer to keep track of time spent on each task or project, pausing it if I leave my desk for even a moment. This means you don't pay for me to get tea, make a sandwich, or take a phone call; you're only charged for time actually spent working for you.
Please be aware that changes to text (copy) can normally be done very quickly, but anything involving a change in the layout (adding an element, moving the position of an existing element, etc) are not only more time consuming but also require time to re-validate the site as well as re-test in various browsers and screen resolutions.