Calculating Monthly Overhead

I've been perusing the vast world of the internet and the best site I've found concerning my interest in computing my monthly overhead was www.creativepublic.com.

HOWever, I still find it to be confusing.

I am not having trouble understanding the formulas but what I am having trouble figuring out is what amounts to put into the following fields:

Income Taxes
This was easy as I did some research on www.salary.com to find out what specific jobs are paying on average. I went with Designer I - Web as my job title and took the lowest salary (more than I currently make) since it seemed to work for me.

Domain Name Register
I figured that for my Web Design business to work, I must own at least one domain name. So I did some research and the lowest price I could find was $65-2/yr ($2.71/mo). One question I have though is I plan on utilizing my first computer as my hosting server, which in turn I will be offering that service as well...to host websites.

Hosting Server
Well, I figured that until I actually get my web server up and running, I will be bound to having an already up and running, as well as stable, web host. Once I get my own server running as I want it to be, then this cost will go down.

Office Supplies
Well, I've never bought office supplies before. I do not plan on actually printing at my home since I do not have the financial means to purchase really expensive pieces of equipment. The only supplies I could think of are pencils, drawing tablets for sketches, large drawing pads for storyboarding. This number should not be too hard to figure out though I could not tell you on average how much of each supply people normally go through.
Marketing
Well, this will be simpler considering I am in advertising myself. I will just need to find out how much it is to place an advertisement on websites and within specific print media. Once I find those costs, I can figure out this number.
Postage and Shipping
Only postage and shipping I could think of is if I need to mail something to my customers, such as their bill.
Telephone
Since I will be running this business from my home, I will probably bypass this service at first. However, I prefer the business line to remain free from any other callers so when I can afford it, I'll add an extra line. Until such time, no cost here.

Accounting/Legal
Do I need an accountant if I can figure out my own finances? What about legal? The only legality issue is registering my business name with the county. Is there something else I should be looking to pay for here? How would Legal be considered part of monthly overhead, unless of course you plan on being sued all of the time?
Travel
I guess the only real travel expenses I might incur is my gas in my vehicle if I travel to meet a client in the local area. This can be easy to figure out since my wife and I already track this.
Office Furniture
Already own the furniture needed though I could really use another desk dedicated to my server and laptop because the one computer desk we do have is too small for me to really work with. I also have other expenses I'm looking at considering I want a bigger drawing tablet since the one I have I use mainly on the go.

Dues & Membership
What dues and memberships should I be expecting? Are they talking about joining up with freelancers where you have to pay? If so, I'm not too sure about that.
Licenses
County business liscense and city business liscense. Anyone know if the State of Florida requires one or the other or both if it is a home base business? Who would I normally call to get this kind of information?
Health Plan / Medical Insurance
Ummm, do I put my own personal health plan / medical insurance bill in here? I'm the lucky one because I do not have this bill yet even though it does come out of my paycheck with Medicare and whatnot. As a freelancer, this is something I will still have to look into seeing how I make sure those are paid as it is supposed to be.

Disability Insurance
Ummm, I guess I do not have to worry about this considering I am solo on this.
Retirement Savings
Do I put my own personal retirement savings in this field? I have mutual funds, so should I be putting my monthly bill in this field?
Multiply by 12 to get yearly OVERHEAD
It says to multiply so I am assuming I add everything above together and then multiply the total by 12 to acquire my yearly OVERHEAD. Am I correct?

My apologies about the formatting of the post. I did some copying and pasting from Excel to this post box.

As you can see, I have much to learn...and I'm willing and able. I do not graduate with my Bachelors of Science in Internet Systems and Software Technology for at least another year and the business aspects of the degree are not until the end. I'm just impatient and I have managed to gain the interest of four companies in designing their website, logo, advertisement slots, advertisement flyers, business cards, letterhead, etc. They've asked that I send them a price list and a list of all of my services and then we'll go from there.

I've been wanting to start my home business for the longest time now but I keep putting it off. So I figure now is time to do it.

Thanks for the help