There is no need for all that , you can register at freelance websites like getafreelnacer.com , eufrelance.com , scriptlance.biz ,etc and start bidding for all web designing projects posted there .
References :

yes, you may follow some legal procedure based on country wise. You may ask the local intellectual proprietary rights for more information.
References :
Hangar17.com

In order to be considered a sole proprietorship you need to be the sole owner of the business. If your friends are fine with that then you can register your business under that title. You can still have employees and hire people on a contract basis, but after all is said and done- it’s really your business. However, be aware that you’re the only one liable for any legal issues that may arise, not your friends. Also, you will have to report any profits or losses in your personal income tax form.

According to the Department of Executive Administration, "All persons engaging in business activity in the City of Seattle are required to obtain a business license." So, yes you will need to get yourself a business license in order to be a legit in Seattle. You can print out an application from here: http://www.seattle.gov/rca/licenses/Licmain.htm

Here is another great website that has lots of resources on starting a business: http://www.gaebler.com/Starting-a-Business-in-Seattle–Washington–Guide

You really need to prepare and do quite a bit of research before starting a business, especially if you want to be successful at it. Also, make sure you write up a general contract for future clients, which you can edit and personalize later on depending on the scope of the project. This is a good way to protect you, your work and your business.

I don’t live in WA so everything I’ve written here was all done from a quick online research. Try checking your local library for more resources.

Good luck!
References :
http://www.seattle.gov/rca/licenses/Licmain.htm
http://www.citmedialaw.org/legal-guide/sole-proprietor
http://www.citmedialaw.org/legal-guide/corporation
http://www.gaebler.com/Starting-a-Business-in-Seattle–Washington–Guide