Your mother may be crying, but she LET HIM DO IT. That house is half hers, and so is the decision to charge you rent. She is not blameless here. Your aunt’s “resources” are none of your stepdad’s business. OP, move out without another guilt pang, okay? Work hard to crush your exams, be super-considerate and make yourself very useful in your aunt’s household (shovel the walk, do dishes, walk the dog, whatever is needed — and if you don’t know, ASK).