It's been a few years since I've lived closer to OU, but I expect that a mid-quality 1 bed/1 bath unit could be had in the 450-550 range. If you want an in-unit washer/dryer hookup, you're probably looking at the top of that range or a bit higher. Traditions Square, the university-owned apartments, provide a fair benchmark (http://traditions.ou...category/10/11/); note that Tradition's rates include utilties, cable, and internet access. Also,a number of new apartment units have been constructed in the years since I've graduated. Undergrad enrollment has also increased too, but at a slower rate; the overall impression I get is that rents have stayed fairly stable, particularly for some of the older units in town (Springfield, Summerpointe)
In other regards, you should be able to stretch a dollar in Norman. Gasoline is routinely 30-50 cents cheaper than in other parts of the country, and food isn't terribly expensive either.