I visited Ithaca in May for one weekend and was able to find an excellent apartment easily. I would suggest starting the search soon, and if possible, coming to look in person. The actual quality of apartments here can vary wildly even within the same neighborhood.I also suggest avoiding Collegetown. Collegetown may be close to Cornell, but the rents are way higher than they ought to be and the apartments are not nearly as nice as other places. Plus Ithaca is small enough that the difference in commuting time to get to school is negligible.Cornell's listings of graduate housing (there's a link buried somewhere on Cornell Law's website) are pretty comprehensive.
Actually, I did end up in a privately owned apartment. Many of the apartments listed on Cornell's site are actually privately owned, but advertised for grad students because the landlords like us better than undergrads. Also, many of the landlords listing via Cornell's site may have other properties available.I live at the very bottom of Collegetown, right where it runs in to the Commons/downtown. I like it immensely. The bus stop is about a block from my place (10 min. bus ride to school/15 minute walk), I'm walking distance from the better Ithaca bars (Commons bars are usually more fun than the Collegetown bars), walking distance from a grocery store, and so on.My main insights on apartment hunting:1. Only look at apartments where the landlord pays for the heating. Don't worry about what other utilities the landlord does or doesn't pay. Make sure they pay for the heat. First off, if they don't, you will get stuck with a lot more bills than you expect. Secondly, if they pay for the heat, they have incentive to have maintained the insulation well.2. If you come looking now, there will be lots of options. This means you can be picky, especially about not renting in buildings/houses that also rent out to undergrads. Most of the landlords here prefer grad students and completely understand why they might want grad-student only housing. Be upfront about it if you want grad-student only places.
Just to throw a couple of sentences about living in Ithaca. As a 1L this year I have been living in Hughes Hall. Despite what some people say, it is not too bad over here. I live in a "suite" with two other guys. We each have our own rooms, but we share one bathroom (although so far haven't had any problems with that). Now as for apartments, I will be living in the Valentine Apartments next year, which is about 10-15 minutes walking from school. They provide a morning shuttle every 20 minutes but you'd have to walk back. I got a one bedroom for $745, but it does not include electricity (and hence no heating is paid for). The electric company here can charge you a flat rate per month which comes to $110 for my apartment. So, my rent next year will be $855 including everything (internet, parking, etc were included in the rent). The real estate agency that gives out these apartments (many apartments available until classes start) is named Novarr-Mackesey. Anyway, do not worry about housing. You can find something the day before classes begin if you want to. You can just take a walk around and ask any of the houses you see about whether they are renting out apartments. They mostly are. Good luck!