How close is this friend? How good is your previous work? How fast do you work? How established are you? How complicated is the project, and what modules are required? How big is the client? How long will the project take? Are designs and specifications provided or will some consulting also be involved? What kind of support do you expect to offer post-launch?

Answers to all of these questions have a bearing on the fee. It's impossible to even give you an estimate without more details.

But the first question I would ask is this: it's all fine migrating a static site to a CMS-based system, but other than that, is there any real purpose behind any additional functionality? Does the site really require a login functionality for the visitors, or is that just there "for fun" or just "because we can"? Don't be afraid to tell your client they are making a mistake. Successful web designers do not just sell a skill, they sell their professional analysis and opinions.

The second question is this: do you really need to use Joomla? I find it is SOOO bloated and hard to work with. I always avoid Joomla, unless there is a specific need for certain Joomla modules. For lighter applications, I much prefer Wordpress or Drupal, or if you have a little money in the budget, shell out for ExpressionEngine.

Don't know how to work with anything other than Joomla? Learn.

Hope this helps.