I believe there's a limit: I'm a programmer, and a PhD student's time is worth a certain amount to me -- at least, as a tutor on subjects I never got to learn

I believe there's a limit: I'm a programmer, and a PhD student's time is worth a certain amount to me -- at least, as a tutor on subjects I never got to learn but have an interest in. After all, most of the graduate students, adjuncts, etc have worked as tutors and instructors. Presumably, this is true of some fraction of other programmers. So you can support a community of some size by selling lessons -- it just requires substantially adjusting the business arrangement, eg, teaching evening advanced math classes that I can easily take 1 at a time of. It's actually near that point -- for what I would pay for lessons, you'd only really need 10-15 students to have an okay job (def: median household income where I live). So there my be some sort of actual logistics problem we can solve with technology here. (As an off-the-cuff idea: Kickstarter an evening class; prepay with limited refunds, etc. It wouldn't cost much for adjuncts to try.)