Hey ya'll, as someone who has a real passion for worldbuilding - in particular crafting exciting environments and creatures, I've created multiple large scale projects over the past few months, mostly to run my homebrew DnD games, but also to help out some friends who wanted to run their own. 

This got me thinking; Is there a market on websites such as Upwork or Fiverr for this kind of product? Or at least is there an interest in the rpg community for people to create paid projects and help out in worldbuilding? I had never really considered anything like this till one of my aforementioned friends told me it'd be a good idea, and that I should really start setting up a portfolio and see what happens. I thought I'd ask you guys first, to see if there's any point in even attempting it. 

Sorry if this seems a bit out of place, I couldn't really think of anywhere else to post it. Thanks in advance. 

This is, ultimately, a business decision, and the good news is you are in luck! There are a host of third-party creators making content. You can study their work and results to understand what you could make in a best-case, average-case, and worst-case group of scenarios. DM's Guild, etc., are good spots to look at the market.

Remember that you would be competing with the major third-party creators, often former WotC employees doing their thing solo or at a smaller company. They are creating worlds filled with content of all sorts - and that's what your "best case" scenario is. Just be honest with yourself about the odds. Can this work? Absolutely. Can you do what it takes to make it work? Only you know!

As mentioned, there are indeed many such places.

And many such things -- both specific to RPG development and more generally for the purpose of of fiction writing or whatever. There are thousands of books and sites that are meant to spur or support worldbuilding -- from entire workbooks with prompts to lists of hundreds of questions, to involved efforts that include structures and systems for selective or random creation.

Worldbuilding is far, far older than the game, and is an entire genre of artistic enterprise. However...

It is not something many folks make a living doing, lol. Even those who take jobs for large videogame companies don't make a lot of money doing it unless they get into a lead world designer role -- and then they need additional skills (such as programming and management, as it is now a team effort).

Now, will people pay for things? The answer is yes. They won't pay much (and never a "living wage" in terms of time spent, or expertise), but they will pay.

Back in the 80's and 90's, a product was released for a low magic world that was stunningly detailed. It was release in small chunks -- Harn is what is was called. It sold "ok" -- and being a low magic, heavily medieval based setting, it was very much a "different" thing, but hard to find. The game company Iron Crown Enterprises released a supplement called Campaign Law, that provided some amazing detail and outline wit good direction and more than a little expertise (for the time) in word building.

DM's guild doesn't allow you to sell custom worlds that are not official; if you want to sell an entire world. For that, the largest marketplace is a place called Drive-thru RPG, which does sell a bunch of different settings for a bunch of different games. Some are system agnostic, others are not.

The area that appears to be doing the best, however, in terms of private worlds, is supportive materials. So, think cultures (but not tied to a race), or economic systems, or stuff that fills in gaps within the rules. Maps of cities, towns, and villages are somewhat popular. 

There are other options -- one can do a kickstarter or similar crowdfunding effort (but you have to use the advertising forum here for any of this to try and get the word out, so you should familiarize yourself with other places as well) or, of course...

you can just put it out on a website. If your goal is sharing, not profit, then that's always a good idea. But if your goal is profit from your work then you have to treat it like a job, and study the community of folks who build worlds as a whole.