I believe they are passed out in the transition days just before classes start in August. As for paying for them, it's just one more item deducted from your pay before you see any of it.
You'll not have need for or opportunity to use one in BCT. But it is pretty heavenly for you and your family & friends, to get those first emails in August! And it was really great to hear from the new 4* who had been posters here when they were appointees.