Silicon Valley is making a big bet on a buzzy, unproven tuition model that would make student debt obsolete. Here's everything you need to know about ISAs.

· Income share agreements are on the rise. Coding bootcamps like Lambda School and WeWork's Flatiron School use ISAs, as do more traditional institutions like Purdue University and the University of California San Diego Extension.
· ISAs take a cut of students' income for a set period of time after they get a job and they come...