Everything I've seen/heard about Bronco says that he is a stickler for rules. Have you heard or have any evidence otherwise? So yeah, it seems easier for me to believe that he was probably unaware that Busby was giving cheap rent to some of the players, than it is to think that he decided to turn a blind eye to it. But we'll likely find out more in time.
Bronco has the squeaky clean reputation, but if Busby was (allegedly) doing this for years and the players supposedly knew about it, I have a hard time believing Bronco knew nothing about it. If the allegations are true then somewhere along the line he had to hear something about it, wouldn't you think?