For many years I made Halloween masks as a year-round, full time job and I have recently moved into dealing in digital art.
I can only reiterate what everyone else here has already said in one way or another. You can make a living doing this if:
1) You love what you're doing and would be doing it anyway, even if you weren't getting paid
2) You're prepared to work long and hard hours
3) You do your due diligence on all your projects: dot the T's and cross the I's :)
And there is a lot more to it than just creating the 3d pieces. So much is market research and accounting. Know your audience. Find voids in the market that you can fill. Do it better than everybody else (at least in your own mind). And know how to value your own work. When I was selling masks, so many of the other independent mask makers would make a new piece and put it up for sale for $200-$300 without any thought to why they were charging that. They'd sell a few, sometimes quite a few. But I did the math and calculated all the overhead and man hours, and realized I could produce the same thing for $50-$60 at retail. And I sold a ton, almost more than I could make by myself, some months.
So talent and ambition are drive are a huge, huge part, but you also have to be smart and aware that you're not working in a vacuum. As well, there is a component of luck involved. Perhaps most importantly, you have to keep plugging away!
To be a content creator requires many different talents, but to me, the most important is stamina.
Say you think of a great idea for a product. (This is already difficult because there's so much content out there). You spend weeks or months making the product, submit it and it's accepted (something that's not guaranteed either). Great. You now have 1 product, and if it does well, you may make enough to cover your costs and time, and maybe invest in some new software/hardware. (And don't forget you have to pay taxes). If it bombs, you start all over again.
So what next? Well, this is where stamina comes in. To make a living, you have to have a lot more than 1 product. So can you keep on coming up with great ideas month after month, year after year? It's not that easy. By the time you get to 5/6 products, ideas start to run out, or they've aleady been done. Waaahhhh!!
On the bright side, if you find a successful niche or style, you can do pretty well. It just takes a long time to get to the point where you can relax. (I've been with DAZ for 12 years and I'm not there yet - lol). But I enjoy what I do, and don't have a boss yelling over my shoulder.
Content creation is something you have to really, really want to do. When I started, making freebies 15 years ago, there were very few handy tutorials. Most 3d techniques were mysteries known only to a few dedicated souls, and I learned everything by sheer persistence. Ask, ask and ask again. Trial and error. Frustration and cursing. That was about the size of it in those days.
Today, things are slightly better for aspiring creators. The internet is a huge resource of knowledge and you can find almost anything if you look hard enough. But you still have to want to do it, and you still need time, energy and talent to be successful. Plus stamina, of course.