I don't live in Boulder, but I am considering CU for graduate school as well, and I can say based on what I have seen/heard in my research of living there, the cost of living would be much more than you are predicting. I'd even go out on a limb and say it would be impossible to find a 3br apartment within a close distance to the University for that price. A 3br in town seems to go for somewhere in the 1900 range, based on averaging the craigslist page. Some might be cheaper, but not 1300 cheap. Take a look at this thread to see what people in previous years have said. Cost of living aside, if you like the outdoors you really can't beat living in a city like Boulder.