To create a new web site, including site map, design, and production, we have a $1500 minimum. For ongoing maintenance and updates, we bill hourly, down to 1/4 hour increments.
Our usual process with new clients is to have a meeting about the site, what it should accomplish, what design and content elements are already available and what needs to be created, timing, special features, etc. Then we do a proposal based on that meeting, and if it suits the client we proceed with the site design.
We ask a 50% deposit on all new projects. Projects are billed monthly based on time spent, until completion. After the completion of the project, we bill monthly for maintenance and changes.