I hate this question, I really do. As an intermediate freelancer who makes money doing what he loves, I get it. As a successful, well-paid freelancer I'd probably still get it. As a famous freelancer/author/etc. I'd definitely get it. To me this is kind of a lazy question and a request for an easy way out.
Which doesn't exist, anyway.
But let's face it, all of us writers have hit that block where we can't think of anything to write. “Writer's Block.” About two years or so I stopped suffering from that problem. How? I'll write another article/blog entry about that sometime soon, so stay tuned for it. It's nothing ground-breaking, so don't hold your breath, okay?
Uh, as I was saying.
I'm really sick of getting the question. I'm sure I asked it a lot as a kid—I'm pretty positive, actually. As you can expect, no one answered it. They were either snappy and short about it or just sneered and didn't say much at all. So you know what? I'm going to spill the beans. It won't make your writing career easy, but it will probably help you out.
Anything & Everything
Yes, you read that correctly, and no, I'm not messing with you. Once you stop stressing and trying so hard, you'll realize that ideas are everywhere. Look at the signs on shop windows, watch a public incident and consider it from another point of view, watch a good play or skim the mags on the local newspaper stand. Once you relax and let the juices flow, you'll start to feel ideas pop into your head. Don't stress— the more you stress, the fewer ideas you're actually going to get.
Whoever called writers “lone wolves” obviously wasn't talking about the successful ones. When writing, whether it be technical writing or fiction, you'll have to understand people. You have to keep them in mind. What they sound like, what they want, what they'd do, etc. You'll also find that in conversations, arguments and friendly debates you'll come up with some unusual or unique ideas. So talk, damn it. Talk.
Reddit, Google, your local newspapers website, you name it. There are thousands, millions, billions of topics out there. All you've got to do is pick something, think it through, research and create your content. Bada-bing! You've got it.
Don't be one of those writers who beats his or her hands on their desk and complains about having nothing to write about. An experienced writer who hears “there's just nothing to write on” will frown upon you, whether you notice it or not, and one who hears you say “I don't know anything special, so I can't write about anything special” will just be outright disgusted.
Now I can safely say, reader—you have no excuse for not having topic material to cover. Now get to it!