Siddhartha Gautama (the Buddha) was (became; established a whole tradition of being) a hermit/beggar/monk; Socrates was a stone mason (occasionally); Diogenes the Cynic lived in a barrel and begged for food; Jesus was a carpenter and then a wandering preacher; Spinoza (as you note) was a lens grinder; Kant was a tutor; Einstein was a patent clerk. And, as you note, especially in the 19th and 18th centuries, many proto-scientists were people with either an established income or independent wealth, who had the freedom to pursue whatever interested them.

We ought to be finding ways to broaden the number of people who can pursue their interests, while not forfeiting security, dignity, and social respect. This is one of the arguments for universal basic income, that it could decouple (some) people's desire to pursue knowledge from the need to earn a living, and maybe even especially from the need to produce regular, measurable results. Right not we're channeling most of our people who are interested in and capable of developing new knowledge into jobs which demand "results" more than they demand that truth be followed wherever it leads, and however long it takes. This will lead to a great deal of dubious Normal Science [0], and very little revolutionary thought [1].

[0] https://en.wikipedia.org/wiki/Normal_science [1] https://en.wikipedia.org/wiki/The_Structure_of_Scientific_Re...