Buddy up with a professor/grad student/research group who will let you steal some cycles.
That’s just so simple, eh? Except, if hundreds of students and research groups require cycles, and the combined computer cluster of several universities is already booked out for months (and wouldn’t even support TensorFlow in the first place, so I’d have to write my own system or port everything to the systems that support supercomputer architectures).
Spending 10 months instead of 1 or 2 and not getting anywhere is also not free.
The problem is that as a student I just can not, in any way, get the money for a 1080. The choice is spending 10 months, or not even starting.