it’s not a matter of not expecting them to do anything. However.
I wouldn’t expect my student dc to pay board.
I would include them in family meals etc, as is normal.
washing if I’m throwing a load on it’s not a problem to add a few extra bits
if there’s a gf/bf as well that doubles the extra food, shopping, bills. Even if they do their own washing that doubles the use of the machine, and if they was daily it’s a pita having to manage their loads and mine. Same with the dishwasher etc. Even if they do their own cooking cleaning etc, it means we’re having to compromise on who cooks when, who needs the dishwasher/washing machine/shower next, those sorts of practicalities.
my own child I am responsible for and will sub their student years, one extra person fitting in family life is not an issue. But another couple in my house? Either they fit in as family, which is more work for me, or they are semi-independent, which means I have restrictions on when I can use facilities in my own house.
a guest for a few days/week? Fine. But 3 months of effectively living in a student house share? No thanks.