Getting Started With Wordpress 3.0 for My Clients

I am looking to use Wordpress 3.0 Multisite for my clients sites as
follows. I want to basically set up one install of Wordpress with the
common plugins and themes (premium and/or custom) that I use. In the
development process I will give them a temporary URL - such as; When the site is
ready to go live I want to just remap the URL to their main URL.

I plan to charge my clients a monthly fee for hosting and managing their sites. I'd like to have different payment plans for different services/space, etc. I figure somewhere between 3 - 5 plans, each with a different monthly charge.

I am looking for advice on how to get started with this. In particular, any considerations I need to think of beforehand as well as any tips on how to do this right.

I thank you for your help in advance.

All the best,