I would say it's not so feasable as a junior unless you really can hit the ground running which only comes with experience, at least in ops. Most clients expect me to be productive within about a week of landing if not less, otherwise they would have found a permie. They also expect senior freelance people in such a space to be making or helping to make a lot of decisions for them, which is hard to do until you've made enough mistakes to learn what not to do, instead of just knowing the latest doo-daa or other.
Finding work isn't hard, you register with a few agencies (e.g hays, linuxrecruit, etc etc and then they farm your CV out to their clients, and then you interview and start working.. I've never spent more than a week looking for a new contract)
As for the amount of work -- endless, at least in devops...
Currently I am working as a senior devops/sre for a startup, k8s, cloudy stuff, big springboot stack (50 or so services across 10 instances, etc) -- I do the same work as the full time staff, mgt treats me as slightly more senior/more votes than those because I am really, but you have to walk a bit of a political line sometimes.
Any questions feel free :}