I bought this Brentwood 7 inch inner spring mattress in mid-June to accommodate my family. Manufacture date can be seen on the tag as shown in the picture. We used it for the following month, and I think it's very comfortable, at least a lot better than the one in dorm. I paid $190 for it and after only three months, I'm selling it for half.
Amazon link: http://www.amazon.com/gp/product/B00C57AIIU/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1

Full Disclosure: last week when I was moving the mattress, I accidentally made 4 scratches on the back of the mattress near the edge (See picture). They are each about 1 inch long and have already been sewn up. I don't think this is affecting any functionality of the mattress, since these cuts are very shallow and only affect the cloth. But I'm still offering the steep discount for this.

$100 OBO.
Cash only.
Preferably pick up at Escondido Village. I can deliver too if you really can't pick up.