The hiring bar is the same and the number of companies in europe that ask much harder questions for 4x lower salary is huge.
European state universities are pretty difficult and the requirements are much harder than US ones. No one hears sob stories - 59/60 is still a fail for 1 point, better luck next time. There are no privileges in Europe for sitting in first row.
It's difficult getting the first client. You mean like Upwork?
The other concern is it would likely look very bad on a resume, did this for one client another thing for another. I'm early stage in career and not an expert on anything yet.
Also, FAANGs in Europe suck and most of their good developers move to the US.