I currently use blender as a hobby, but I consider freelancing as a possible path in my future. So I would love to hear some of your thoughts on the subject. For example I read that is nearly impossible to freelance as a VFX artist in Blender since it’s not an industry standard
You have to consider what part of the process can be done in a separate program and not mess up some pipeline. Asset production (Model/UV/texture) for instance is a job that can be done in any program. All the studios that I’ve worked for, don’t care if you model in Modo, Max, Maya, etc as long as you can do the job. Your reel/portfolio will be the proof of that. As far as the rest of the process, I’m not sure but if your FX look as good as hollywood movie FX, I feel like it might be possible. Assuming they can be output in an industry standard format like .VDB or .ABC. Not sure about that though. I know there are artists here in Hollywood who use Blender for compositing and one off VFX.
Animation/rigging is totally out of the question though. 
Currently what Blender is used for is : short films, series, some ads, some archviz (as far as I know). Because of the limitations that we know, it’s definitely not used for anything that might involve, say… crowds or extensive simulations or really anything hugely complex - I mean as a main software at least, however…
It’s a good modeler. And has a great rigging toolset, too, and Cycles is a more than decent render engine - so ideally as long as your part of the pipeline is blackboxed you could theoretically use Blender : this is true for small teams only however, you probably won’t sneak Blender into the pipeline at a big VFX house unless your area is kind of pipeline-agnostic (modeling/sculpting is a good example, sims, maybe some rendering - so definitely not animation).
I think people like Pitiwazou might be of better advice than me here cause they actually make a living using Blender - I get to use Maya mostly because I am a rigger/animator.
However I should point out that I did in fact introduce a past workplace to Blender : we used RBDs for falling rocks, rigged an entire dino for a promo shot of the film, all in Blender, because it was so damn fast and the rigging lead was unavailable at that time.
However apart from the packshots and all, recently the fracture modifier branch was used for the Fortnite trailer, a few years ago Cosmos Laundromat director made these mini-series for TV where everything was made in Blender (tracking, animation, rendering, comp)… those are just a few examples.
I think there are several possible ways : either you are a freelancer who operates in packshots, animated logos and jingles and whatnot and you can totally use Blender for the entire thing since you don’t have to answer to anybody, or you’re a modeler who freelances for bigger houses punctually - or you try to find - or create - an animation studio that uses Blender all over the pipeline (since animation is what it’s best at).
It’s not a complete picture, others should chime in.
Hadrien
its also used in 3d printing a lot, if your into engineering it might be something.
Really interesting and informative answers, thanks people, have a nice day.
Since blender is the only viable 3D app everyone would like to tailor for personal needs, I think customisation and scripting would be the best area to catter to a global market, but if you work locally, then modelling and rendering.