Buy Cheap FutonOkay so you need a place to sit in your dorm room and it would be nice if the piece of furniture could do double duty.
You can buy a cheap futon here. Maybe even a gently used one for sale. Most futons are full size. You probably won't have room for anything larger. A new cover would be nice if you are buying used, to spruce it up a bit. They fit nicely under a loft bed, or against a spare wall if you can manage. It will be nice to have somewhere to sit besides a office chair and your bed.
Have a look at these. Ask questions of the seller. Know what you are buying and don't forget to ask if you can have it shipped to your dorm room. Never hurts to ask. Find out how easy it is to buy cheap futon.