There are plenty of schools, ie. DCA & PanAm, that would be happy to take your money with the promise of hiring you as an instructor when you finish. This is the case at many smaller FBOs as well. Like anything else, I think it is being in the right place at the right time. I was instructing at an academy (ATA) that closed and ended up at an FBO making twice the pay, but half the flight time. Meanwhile, friends of mine were working for free (painting, cleaning, working the customer service desk) at flight schools in the hopes of getting a CFI job.
If you are flexible on where you live, my advice would be to get your instructor ratings as inexpensively as possible and then go find a CFI job. Don't get your mind set on instructing where you got your ratings because I have rarely seen it work out.
Don't give up and things will work out.