That's why these bootcamps only charge students after they complete the course and get an industry job.
Quoting that Fast Company article: "With the support of his wife, he sold his 2004 Volvo for the amount of tuition, and his family of four in the suburbs made do as a one-car household."
Quoting http://www.hackbrightacademy.com/faq : Tuition is $15,000. If you receive and accept a full-time job offer from one of the companies in our network then we will refund $3,000 of your tuition. If the program doesn't meet your expectations in the first 2 weeks, we'll give you your money back (less your down payment).
Yes, there are some which do as you suggest. Quoting http://www.appacademy.io/#p-program : App Academy does not charge any tuition. Instead, you pay us a placement fee only if you find a job as a developer after the program. In that case, the fee is 18% of your first year salary, payable over the first 6 months after you start working.
But certainly not all do as you believe they do.