Right, the same Rusty who throws alcohol-fueled parties on campus which involve underage drinking, is aware that Tommy and other DIK members are smoking weed, engages in solicitation of prostitution with the Pink Rose girls, and is such a wishy washy leader that he immediately defers to a freshman who's been a DIK for less than 24 hours when faced with the prospect of cleaning up the trashed mansion.
He ignores all those rules, but militantly follows the "only DIKs live in the mansion" rule.
If MC went up to Rusty and said "Hey, Sage is gonna stay with us for a few weeks while she gets her situation sorted out," Rusty would probably cave in immediately and agree.