Off campus housing is expensive in Collegetown (College & Dryden). Studio apartments are going to be around 1000, usually 1000+. If you have roommates, 700-800 is usually the norm. Most people (undergrads) sign leases in the fall for the next fall--so the prime real estate gets grabbed up really fast. Once you decide, you should look for an apartment ASAP! Although there are still good apartments later in the year, they are harder to find in Collegetown.
The downside of Collegetown is that there are a lot of undergrads. A lot of houses are really beat up because of parties and people not taking care of them. Most houses are old. Although a plus is that most places are furnished.
Housing gets both nicer and cheaper the further you head out from Collegetown. A lot of grad students I know have apartments in the Commons. Housing really isn't very expensive in Ithaca. You can get a huge, beautiful, clean apartment for 400/500. If you have a car or don't mind using the bus, finding a place far away from Collegetown may be right for you!
Alternatives to Collegetown, cheap but still within walking distance: below West Campus, downside: you have to hike up the Slope everyday to get to campus, not pleasant, especially when it's snowy and icy which is the majority of the Spring semester. North Campus, downside: far from main campus, count on a good 25+ min walk (though depending on where your department is). You can usually find nice, well kept places around West and North campus. I'd say rent will average 600 in these areas.
I did my undergraduate at Cornell. I lived in Collegetown for three years. I absolutely loved it, even though I paid an arm and a leg for my not-so-nice house--I shared it with a bunch of my friends and we all had a blast.
Most grad students I knew didn't like on campus grad housing. Cornell put all the grad students in dorms REALLY far from campus. I do not recommend them at all.
A car isn't necessary in Ithaca. The bus runs pretty well. But if you don't have a car, I recommend making friends with people who do. At least for those weekly Wegman runs.
Parking is expensive near Cornell. The University itself charges crazy amounts of money for a parking space on campus, couple hundreds of dollars a semester. And space is limited, so even if you are crazy enough to be willing to pay Cornell hundreds of dollars for a parking space that's going to be far away anyways, you might not get one! Senior professors get the spaces near their buildings, everyone else have to walk a good 10/15 minutes to their parking lots. Parking is also expensive in Collegetown, it's around $500+ a year in addition to your rent. So this is another incentive to get a place further away from campus--free parking!
There are surprisingly a lot of stuff to do in Ithaca for amusement. Lots of festivals going on: Brewfest, Chili fest, Ithaca fest, Apple fest, GrassRoots musical festival. You can also take wine tours--lots of wineries around the Finger Lakes. The Collegetown bars are pretty packed on weekends. I've heard good things about bars in the commons too.
You think you are going to visit to NYC or Syracuse or something, you are not. It's really difficult getting in and out of Ithaca. During the semester, you are going to be so busy, you'll be lucky to even show your face around Collegetown. I wouldn't plan on doing any inter-city traveling, maybe during the summer!
Snow and ice are always removed promptly. Roads are kept clean. The university does a great job of sweeping roads and walkways around Campus too. Most of the time.
The airport is expensive to fly in and out of. It's also a bit of a hassle to get to. I think there are only connecting flights to Philadelphia and Washington DC or something. There are only a very small handful of cities Ithaca connects to. Most likely, wherever you are trying to get to, you are going to fly to a city that is in the opposite direction in order to connect to the city you are actually trying to get to. In short, save yourself the time and money, drive to Syracuse or Rochester and fly out from there. You can also take a bus to NYC (there are lots of buses to NYC from Ithaca) and then fly from there. If you live within driving distance, I highly recommend driving. (My family lived in Boston while I was an undergrad, I always car pooled when I needed to get home. The only other way to Boston from Ithaca is flying out of Rochester. Seriously.)
Anyways, hoped this helped!