Making decent money writing for other people is not tremendously difficult, but I see a lot of new people making the same mistakes. Now, I don't know everything, but I do know a few things. So here's how to get your article writing business off the ground.
Treat It Like a Business
This more an attitude thing than anything else, but if you want to make an actual living at writing, you need to treat it like a business. You need to take hitting your deadlines seriously, you need to have defined daily goals and you need to think of yourself as a professional.
On the more concrete level, you also need to have some sort of structure in place for dealing with your income and keeping track of expenses. You will need to pay taxes, and keep this crap straight is a lot easier if you have that structure in place from the start. I use Quickbooks and an accountant.
Get Someone to Evaluate Your Writing
Before you start writing, you should get some idea of whether you're any good at it. Writing is interesting in that almost everyone thinks they can do it, possibly because they do some form of it everyday. While writing well enough to get paid for it isn't any more difficult than, for instance, learning to drive a car, it isn't something that everyone can just do.
Ideally, you should get someone, or multiple someones, who knows about writing to evaluate your level of skill. They can tell you where they're at and what you need to do to improve.
Here's a bare minimum test: Do you know the difference between their, they're and there? Your and you're? If you don't, you have a long ways to go before you even consider writing for anyone else.
It wouldn't hurt to buy a copy of Strunk and White's Element of Style, either. You can probably find it for free somewhere on the internet, and it's going to cost maybe a buck on Amazon.
Learn the Basics of Copywriting
Copywriting is writing to persuade, convince and sell. Even if you don't intend to write sales letters, you should have a grasp on how it works. The side benefit is that many of the people that will hire you will want articles that will convince the person reading to at least click on the link at the end, and knowing how to persuade is going to be helpful.
But the real reason you should know something about copywriting is because you need to be able to sell yourself. Take a look at the Warrior for Hire section and read a couple of the content ads; what you'll find is that most of them are basically a list of prices. They don't demonstrate any particular reason to hire that writer beyond price, and believe it or not, writers are not commodities.
This post will be long enough already, but the most basic thing you need to know is AIDA, the acronym or possibly mnemonic for the four things you need to do in your copy:
A - Attention. You need to get them to notice that you actually exist. You need to get them to read the rest of your copy, so this is largely going to be a matter of your headline and your opening.
I - Interest. Once you've got them, you've got to keep them. You need to know how to hold their interest.
D - Desire. Make them want what you're offering. Tell them what you can do for them, what problems you can solve, how you can help them profit.
A - Action. Tell them what they need to do, which in this case would be hiring you.
Build a Portfolio
Are you writing everyday? Or at least five days a week? You should be. You need to have a portfolio to be able to show people, especially if you want to charge rates that will actually help you make a living. Stuff that has actually been published, either in the real world or on the web, is best, but just a sampling of articles with different topics and voices is fine.
This is also important because once you get started, the nature of this kind of writing means that most of your clients won't be keen on your using your work for them as a sample. Nothing wrong with that, but it does mean that you will need something else to show off.
Another copywriting concept that is important for your business is social proof. Basically, this is people recommending your service as evidence that you don't suck. You know how you get testimonials (or reviews, or whatever terminology you like)? First don't suck. Second, ask. If someone likes your work, ask them for a testimonial. Not everyone will give you one, but many will. If really don't suck, you'll get testimonials without asking, which is nice.
Know and Sell Your Worth
Here at the forum in particular and the internet marketing world in general, there is a lot of price competition. Any time writing prices come up, you'll get people saying that five dollars is plenty for a 500 word article. What this has created is a world where writers are afraid to ask for decent prices for their work.
As I implied before, you shouldn't be competing on price, and you certainly shouldn't be racing to the bottom. If you're good enough to get paid for writing, you're good enough to ask for a reasonable rate.
The rock bottom minimum I would suggest is $10.00 per 500 words, and that still isn't really a reasonable rate. But if you can't get that, you either aren't very good and should probably try something else or, more likely, you suck at showing people why you're worth it.
You need to show your potential clients what you can do for them and what makes you better than cheap, cheap writers. This is an aspect of copywriting and the inability to do so, and combined with a lack of awareness that you can charge more, is one of the things that keeps writers from earning halfway acceptable money.
Confession: I am still not as good at this as I'd like. One of the things that is going to affect your reputation and your ability to earn is whether or not you can hit your deadlines. The primary cause of this is overestimating how much work you can do.
My advice is to actually see how many articles you can comfortably do in a day, subtract an article or two from that number and use that as a guide for how long it will take you. Take weekends off. It's always better to deliver your work early rather than late, so give yourself some time padding.
There's probably (definitely) more but this should get you on the right path.