When you improve the quality of the stuff and not use as the University gave you - you have to pay for the extra value of higher quality beds and anything you add to the dorms. You can not get bills by using the dorms just as they are most likely. At least that is the way it was in Sims 2.
My sim did not go the dorm route this time though, instead I took and bought her the little starter house and until I increased the furnishings, added a thermostat, etc my sim lived real cheaply and then I upgraded her furnishing etc so it cost her more. So that is how it worked in the starter house with no roommates or anything - I am sure the dorms charged bills for better quality stuff too and why you pay bills. I'd rather my sim pay bills then try and live on low quality beds and she get kitchen appliances in the starter house - so food cost her money too but she gets skill and always happy with her food. It is still cheaper then living in a regular neighborhood in your own house - and my sim never has to move out like the dorm livers do. She has a permanent house in college town if I so desire.