Surely all you need to ensure is that the rent you charge the occupant is no less than whatever you're charged for living in your military council house?
Back in the 1970s when money was much tighter, 4 of us rented a house from a Sqn Ldr who had been posted to Germany. When he was promoted to Wg Cdr, he told us that he intended to put up the rent; however, we told him that it wasn't very fair to expect us to pay for his promotion! A little research revealed that he was doing quite nicely out of the 4 of us since he wasn't being charged much for his OMQ in Germany..... Having called his bluff, he agreed not to increase the rent!
I'd be wary of posting any "A mate told me I could claim" stories - they cannot be verified and may queer the pitch for others.