Which media has the lowest barrier of entry for creators? Not including fanfiction.
Honestly either Blogging or podcasting.
Podcasting needs a microphone. And previous acting or vocal experience or a naturally nice voice helps but isn't essential if you are funny.
YouTube would need that as well as either a camera or the ability to animate in most cases.
Blogging means setting up your own website or using a blog service. Which does have a learning curve and ongoing cost.
But doesn't really take space.
If you like writing an decent alternative to blogging with less upfront costs is making an email newsletter. So long as it has a clear value proposition.
Those are both usually non-fiction writing based in terms of domain. Although, I guess you could have a creative writing newsletter?
You could try non-fanfiction writing on royalroad or something? But that seems fairly similar in some ways. that isn't super hard to monetize although it is hard to live off of.
Youtube is similar but has more costs. (But more discoverability.)
Streaming is an option, It is less intense equipment wise than youtube overall.
However it does mean you need a nicer computer so if you don't already have a decent graphics card then it is very meh.
If you already have a creative skill there are synergies there.
In terms of monetary cost, Making your own music with a DAW on a computer is probably the lowest cost barrier. But that either takes a lot of time, or music skills to get anywhere.
You can use something like LMMS and get started pretty well even with a garbage computer that is like 10+ years old.
If you watch some youtube videos and such you can probably make some stuff that is kind of okay. Particularly if you learn a little music theory.
You don't actually have to be able to play an instrument to make music but it helps.
If you can/want to sing or write lyrics that is hard and more of a later thing that requires a mic, But you can get pretty far without lyrics.
If you didn't have a computer and just a phone or something art would be competitive for time and cost. But that is more directly competing with AI. It's not computer dependent but requires more physical materials and such. (Or maybe an art tablet, Which is on the low end on par with a meh mic.)