If you want to work full-time on open source, then you need to treat it like a job. Either find an employer who will pay you, or start a business and become your own employer.
One way to start an open source business is to use a public/private licensing model, a.k.a. dual licensing with an 'open' license and a commercial license. The key is that you can have readable, modifiable, redistributable source code, without universally giving your work away for free. Instead, charge a fee for the right to use your software to create proprietary software, or for the right to use your software in a commercial context.
License Zero is designed to support developers pursuing this kind of business model. There are two public licenses, Parity and Prosperity, and there's a payment platform to charge for private licenses. https://licensezero.com/
Parity is a copy-left license, and is best suited to developer tools and software libraries. https://paritylicense.com/
Prosperity is a non-commercial license, and is best suited to end-user applications. https://prosperitylicense.com/
The Sustain podcast has an interview with the creator of License Zero, Kyle Mitchell. https://sustain.codefund.fm/29