I believe many of us are doing it for a living.
What you can earn depends on many factors. Firstly, it depends on how good you are at what you do. Secondly, it depends on how well you're able to market yourself. And thirdly, it depends on where you live.
Of course I'd recommend a career in web design! It's a wonderful job because it's so varied and rich.
You should be familiar with what related skills are expected of you, e.g. various frameworks and markup/style "helpers" such as SCSS/Less/Stylus for "rapid CSS development" or even HAML (if you work with Ruby).
Here are two examples of things I have begun designing recently. It's a challenge for me to finish a design when I'm not doing it for anything but fun and practice. I wind up not knowing what to put on the site because I don't know what industry it's supposed to cater to!
That may not be the most practical approach and the reason you're finding it a challenge to finish the design is due to the fact that it's never a good idea to just fire up Photoshop and play around. Of course you should play around, but you need to know what it is you're actually doing. So, I'd start off with writing down a small brief on what the site is about and what it is supposed to do, what features it has and what audience it is aimed at. When you have that down, create an information architecture, a content structure. You can do this with a pencil an paper, there's no need for high-tech at that stage, but there are tools for that. The most efficient tool is a good and solid text editor. You would get straight to coding (HTML and CSS) and that's a good way to get right into one of the main pillars of the craft because, as a web designer/developer, your time will be mainly spent writing code.
I have all the time in the world to practice my web design skills. I've got the entire Adobe CS6 and a lot of ambition. When I do get a new job, I hope to make it temporary until I'm able to break into the world of web design as a career.
For books, I can recommend pretty much every book that's been released by fivesimplesteps.com and abookapart.com. SitePoint has quite a few good ones as well, so that's another place to look. And there are so many others, but the first two resources are quite good to start out.
tutsplus.com and its entire network have some fantastic courses. I can definitely recommend them. Learnable.com also has some really good stuff, so that's another resource to check out. Also check out sites like css-tricks.com or smashingmagazine.com that offer a broad selection of tutorials, snippets and walkthroughs.
For WordPress specifically, I recommend perishablepress.com. In my mind, it's the best online resource for WordPress related topics. Jeff Starr, the owner of that site, has also written a highly commendable book on WordPress called "Digging into WordPress".