Maintaining a site
Once you have a basic site built you will want to make changes and keep it up to date. Most developers do site maintenance for a set fee. The going rate seems to be around $100/hour + from a professional agency.
When you have the site designed you can also ask for dynamic pages that allow you to change items such as event calendars, biography pages, and special promotions. The site will have special pages that you can access with a userID/password allowing you or someone in your company to change blocks of text without needing any knowledge of XHTML or web page development.
Content Management Systems (CMS)
There are open-source (free) frameworks available such as Drupal that allow a developer to quickly build a site with login privileges. You or your staff can easily add/change content without having to know XHTML.