Easy to ask, hard to answer dude....
Understand there are 10's of thousands of people with the same idea!... Don't mean to bring you down on the idea but its bad, ready bad....
3 Basic options
Freelance - A pro with 20yrs in the game and a long built reputation for good work and fare pricings.. could make a living... To 99% its random and best thought of as a hobby that drops a little cash now and again...
Corporate - Mc Donalds, Nike, Ikea etc.. You work for 1 specific business.. today you change the pic's the prices and content given to you by marketing.. tomorrow, you change the pic's the prices and content given to you by marketing... getting the idea.. Its safe its steady its data entry... very average pay.. best chance!
Design Firm - Usually made up of teams of about ten.. Each having specialty skills for different parts of a project.. Front-end Back-end & Graphics.. smaller rolls, law, consultants etc...
Im Australian and you have to be in the major cities to be in the game.. Here that's
Sydney is home to me.. so know the game well... in a City of 4 million people only about 5 Web Design Firms are doing well... calculate your odds on getting that job?
Think very hard about this choice dude.. If your a family man it just many not be an option kinda stuff...
If you want to continue to pursue the idea, then yes make a portfolio of projects.. Fully functional on-line demo's (real if poss by any means)
- 3 x very different looking Wordpress sites
- 3 x very different looking Joomla sites
(use extra plugins to customize and show skill/understanding level)
- 3 x Responsive templates (for phone, Tablets & PCs)
- 3 x Code from the ground up yourself displaying custom/unique design and skill level..
(have both some PHP & ASP in there)
- 4-5 Apps for both Apple ios & android
So show you know a little bit of everything, then specialize in 2 or 3 you liked.. If it graphics than your going to need to know at least 5 programs like photoshop for different things.. There is only so much 1 human can do.. and its to much for 1 person any more.. when was the last time you saw the word Webmaster used?... As extinct as the dinosaur....
Think it over mate... Luck