Well, I read this post a few days ago, and wanted to answer, but decided that I should think about what I want to say in response to it. This is without a doubt, a touchy subject for many people to talk about. And I've decided that I am going to talk a bit about freelancing, but not touch on rates. Sorry guys.

So here it goes.
Freelancing is a term I hear thrown around the cg community quite a bit. And what i've noticed in my few years of doing this is that there are two kinds of freelancers. There are the freelancers that are outside of major industry epicenters, and the other freelancers that live in places not known for their cg production industry. This being the case, pay is different in each of the two based on budget alone. That being the case, you also have to factor in experience level. Many companies will have a small budget and go after "freelancers" outside of the epicenters because they feel that they do not know anything about the industry, and this is often true because unless you've worked in an "epicenter" as I like to call it, you can't know because you haven't worked there, and if you have, then you know that it is different because it's a different ballgame in many respects.
My experience outside of epicenters has been this, you live in somewhere far away from where many of the projects are being done, and so you get many fringe companies, opportunities presented to you, you are young, trying to get experience, and are willing to trade work for experience, this is to the companies advantage, and being older, wiser, and feeling like they hold the keys, they know that they are in the power position. So they will try and get your work from you for as cheap as possible, and this is a universal concept. However, you work from home, and use your own equipment, and possibly don't have the resources you might otherwise have to solve weird problems. So in a way, you are really on your own, and the market is pretty thin. All these and many more factors can add up to a fairly hostile environment that may leave you feeling pretty sore when a job is all said and done.
My experience inside the epicenters has been an entirely different one as a freelancer. Most places in an epicenter who hire freelancers are established places getting work from big network clients who want quality work, and want to be able to ask for more from their vendors. I happen to like this a bit better because:
A: it pays better without a doubt
B: You usually get to work on a machine that's lightyears better than what you have at home
C: You get to work on cool projects that you will see on tv or big screen.
D: You get paid to network and make more clients for yourself. And this is a big one because people start calling you instead of you hunting them down.
E: The creative environment working with other people is much more stimulating than working in your livingroom/apt/ect. And will spur your growth as an artist and force you to step your game up or you will sink.
F: You are empowered as an artist because you get put into a position where you are hired on because they need a good artist, not because you are cheap labor and can get the job done.
That being said, I don't mean any disrespect Mahmoud, but if you are asking the kind of question like how much should I be charging, then maybe you should be hitting the bricks and getting your feet wet before you try to start a company. I think it's an awesome idea, and an excellent goal to have, but I think if you don't know what to charge then maybe you should be getting some more experience, and earning your position rather than just providing a service without really knowing what goes into it fully.
So instead of quoting rates or anything silly like that, i'll provide you with a basic formula similar to what's already been stated on this thread.
How much is my rent per month, I should make this in a week at least. and if I cant, then I should get a different job or smaller apt.
Am I using my own machine?
Am I driving to/from work?
Luxury? What do I need to be happy? be realistic. the operative word here is NEED.
Also, how booming is buisiness where i'm at, think supply and demand.
And finally, how much experience do I have? Have I been doing this for 1,2,3, 15 years? if i've only been doing it for one year, then I don't have an incredible reputation yet do I?
All that being said, you will prob give your client a number that will inevitably make them crap, but then you come to a compromise that will make you both happy, and that's how it works. There are always exceptions to the rule, and it's never good to assume you are that. That being said, It's always good if you're not in an epicenter to get at least 25 % up front and then only deliver proxies with watermarks on them until final delivery and you've been paid. That will prevent anyone from taking you for a ride. And it will also let them know you intend on delivering a product but that you are serious about contractual obligations. Many companies handle things this way and it's a great form of advertisement for you while being an informative part of the process. So yeah man, I hope that was somewhat helpful.
-Z