If you don't go for a CMS, and you want the client to do his own content updating, you'll end up having to create your own mini-cms. This will entail an admin area and a WYSIWYG editor for updating said content. That said, updates can also be done via FTP file update, circumventing online editing. As far as projects go, it isn't too bad, but if you don't have the experience of dealing with security, SEO, etc, it may take a LOT longer than you envisage. Integrating an open-source e-commerce system may pose technical problems as well if you're using a custom system. However, there are good robust systems out there that may suit you.

CMSes like Joomla have e-commerce extensions. You should investigate these CMSes before flatly deciding against them. Spend as much time as possible looking at the use cases and essential functionality required. Decide whether you and your partner are up to the task of completing the work in the time available, with a custom setup. Be aware that all CMSes also require considerable time to get to grips with the way they operate - some have steeper learning curves that others.

I don't understand your wish to keep using Dreamweaver and avoid using the CMS templates. All of the CMS's that I am familiar with have templates that provide the front-end look and the interface to the rest of the system. The free ones generally use some combination of php, html and css. You may want / need to make modifications or build you own templates from scratch and that might be the only place where Dreamweaver might fit.

I have built web sites for people who aren't very high tech. They have been able to maintain them on their own with minimal help from me. I looked at all the best known CMS's and decided to stick with Website Baker because I find that it is simpler and more straight-forward then the others (to implement and to maintain). I suggest that you look at it and compare it with Joomla, Drupal, Wordpress and the rest. Each system has it's fans who will claim that their CMS is the best. There is no definitive answer. Most CMS's have some sort of e-commerce plug-in. That might become a key distinguishing factor as you will need to match up your e-commerce need with what the various systems provide.

I second chrishea's answer. If you're going to use a CMS, use a CMS. Tinkering with a template in Dreamweaver is probably more complicated than it sounds. Before you start dissecting a template, or even devise one from scratch, you need to know the system inside out - a number of CMSses I've used, don't simply have a plain html page, but a php object-orientated system for providing output - which, unfortunately aren't always implemented as a model-control-view system. Modifying template elements through the interface should be easy - colour schemes, background images - that sort of thing - a noob could do that.

The Ardav and Cherishea answers still concerns. But I would add that, if your friend have some knowledge on PHP and have guts to face the issue he can use some frameworks. I was looking at CodeIgniter video last night. It is really simplified even for non mega-PHP-know-how. If that is hard the only best plan B is given by Ardav already :)

On this websit you can playaround with most cms, blogs etc to find the one you like
http://php.opensourcecms.com/

I don't understand your statement because the only look that the CMS has, independent of the website look provided by the template is what you see in the back-end admin facilites. Some CMS's even have separate templates for that. You seem to have focussed on Joomla and that's ok if you know that Joomla is what you need / prefer. I don't have the impression that you've done enough research to reach that point.

You're right that the standard templates tend to be variations on some standard format formulas. You can build your own template to be almost anything that you want it to be if you have the knowledge of the CMS interface requirement, PHP, CSS and so forth. If you look at some of the galleries of sites developed using various CMS's you'll find some very customized formats. The user interface won't change regardless of the template layout (at least for text and picture content). If you want to get into introducing a lot of javascript / ajax features, then it will depend on the support provided by the CMS and how integrated it is with the other CMS capabilities.

I believe that you can do almost anything within reason using a CMS if you are able and prepared to do some customization. You get a lot for free using a CMS but if you are a skeptic or if you really like to do things from scratch then it may not work for you.

I'm building my own CMS (alone, from a scratch, with exception of borrowing account management from phpBB-forum, and MySQL-class), and I can say that making "mini-CMS" is relatively easy. While on the other hand, the more editability for appearance it has, and the more easy of use it has, the more work it demands. My aim is to make fully customizable appearance with ability to write content without a need to know anything about (X)HTML or CSS (I bet BBcode rings bell), and I can say that I'm not even half-way, and I've worked with the frame for over a year.

One way to really learn the stuff is building something (least) "semi-big", like mini-CMS, and taking advantage of things like AJAX. :)