The only thing I have to contribute is tons of studies pay people for their participation. Medical studies are always posted on campuses and local stores for pay, or at least they used to be. There's a whole platform (Amazon Mechanical Turk) that hosts research groups from Duke, Yale, Princeton, Harvard, Oxford and tons of others who posts studies all day, every day for payments ranging from a nickel to over $100. And many have screeners for certain attributes they are looking for (history of mental illness, age, sex, family size, job status, marital, etc, etc). I do mturk as a side gig. They pay students who are on campus much more for the same things.