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Most PhD programs worth a damn will waive tuition and either provide students with a stipend or research assistantships, teaching assistanships, etc. That's how I got my PhD (never could have paid for it!), and that's how all of my academic friends did theirs. If you're looking at programs that want you to pay big $$ and will not provide ways for you to make a living, look elsewhere. In the sciences, it's absolutely standard that you will not pay tuition and you will receive stipend support for at least several years. It's tougher in the arts, but there is still finanical support at good institutions. Also, there are many government and private grant opportunities for PhD students in every area - no guarantee you get one, but it's certainly worth applying.
That said, grad students don't make much money with just stipends or assistantships, and it's no crime to get outside work if you can juggle it all. But like the previous poster mentioned, if you do adult videos, that's out there for the world to see forever - you'll have no control over that material. That might mean future employers and students will come across these videos, so it's really something to think about.