Copywriting can be very lucrative for those who are skilled at it. Copywriters are responsible for all that great writing you see that hooks you in and makes you want to purchase a product or service. Effective copywriters know how to "hook" readers, draw them in and use their words to inspire action - buying, signing up, whatever the case may be. Copywriting is a true craft, an art that requires a lot of practice and a large time investment, however it is one of the most lucrative writing fields in the world.
Copywriting effectively is a great way to market your own products or services as well. Imagine the possibilities, not only are you able to earn great money writing sales pitches and marketing materials for others, in your spare time you can use this skill to develop your own website(s) and market your own products. See the ebook section for some ideas. Information is a hot selling product right now. If you know how to do something well, can answer a question or solve a problem, and have the copywriting skills to hook readers and get them to pay for your information products, you have the potential for great earnings.
One of the greatest copywriting niches out there requires very little writing at all - headlines. Headlines are 10 words or less and are used to compel a reader to believe they need to see the content of that ad etc. Think of "pay per click" ad campaigns etc. The goal of the business is to get conversions and the best way to do that is extremely compelling copy with very tight character/word limits. You may be writing less - but every character has to count! If you can master this technique the earning potential will be sure to follow.
Copywriting is competitive and can be difficult to break into, the flipside to that however is that there are an abundance of opportunities. Think of all the companies out there that can stand to benefit. You will have no shortage of leads to get started, and once you are established word of mouth advertising is a copywriter's best friend. To be successful as a copywriter you need to have a strong portfolio with examples of what you can do to show prospective clients. You may also want to get some experience under your belt by working for an advertising agency for awhile first before going solo.
Copywriting Blog Blog that presents the basics of copywriting for free, discussing the importance of winning headlines, hooking readers, and more
Ten Commandments of Copywriting Simple, informative and very true - if you can do these you can write great copy.
*Copywriting 101 This website is an excellent, in-depth introduction to copywriting, how it works, and how to develop skills in it. Very nicely done hence the * :).
Here is a video with good examples of powerful headlines that have been successful