I've made my living based on OSS projects for almost my entire professional career (about 17 years, specifically working on Squid, SciPy, Webmin, Virtualmin, etc.). Not a
great living, mind you, but it's kept me in food and houses and given me a lot of freedom. Also, most of the stuff that made money hasn't been the stuff you want to be doing; the code doesn't make money, in the vast majority of cases. It's the stuff you do other than code, but that requires deep understanding of the code, that makes money. Deployments, support, customization, packaging, documentation, bundling and "productizing", and occasionally getting jobs on the strength of your prior contributions. I've written a lot less code than I would have liked in all those years, and much of the code I wrote has been fleeting ephemeral things like shell scripts and packaging scripts.
I don't know a lot about the frontend OSS world, but I know that if you pick a project that has a lot of money being thrown around (in large deployments, for example) then you'll find that it's easier to get some of it to land in your pocket. Niche projects are difficult to get paid for, but can be good places to learn; smaller projects may be happy to have some help and will lend more guidance when you ask questions. But, then again, some big projects have people specifically tasked with bringing new developers up to speed and "community management", so that may even out that difference.
It will never hurt you to have OSS contributions on your resume. It's gotten me jobs, and has allowed me to round up good paying contract work when I've needed it (even in unrelated fields; I've recently done some Ruby work, even though I've never had a real project in Ruby). And, as someone who has hired people, I can say I've only ever hired people who had OSS work I could see. Sometimes unrelated to what I was hiring for, sometimes they were already working on what I was hiring for and I just wanted them to be able to spend more time on it and get them on board with the company road map.
All that said, it's not the easiest way to make a living in software. Getting a real job is probably the easiest way, and if you're lucky you'll get to work on OSS stuff to one degree or another. I've worked on tons of stuff that I never got paid for, and don't expect to ever get paid for. And, if you aren't really directing your efforts toward making something pay, you're unlikely to find that it'll pay.
OSS contribution does not, in the general case, lead to getting paid. But, it can lead there if you want it to.