Creating a sole-proprietorship

I want to create my business that is ran exclusively by me. I want to register my business name and begin marketing my services. Do I file a DBA or a sole-proprietorship? What is the typical cost in doing so? Do I need a federal tax ID? I want to do what is right, but at the lowest cost.

either way is fine

See Starting a business: Starting a Business for general background information and http://www.sba.gov/index.html

I suggest you to make LLC other rather then doing it alone. There are many benefits of incorporation. Incorporating a business also means that your corporation can deduct business operating and capital losses with more ease than a sole proprietor can. For more information about incorporation you can check this site: http://blog.clickandinc.com