I would start looking about two months out. There are many people who list through the MLS (multiple listing service) that rent out investment condos, or rent if they cannot sell. These listings, only licensed brokers have access to. Often these properties are less expensive too because people are only trying to cover their mortgage. I would be happy to send you some of these properties when you are ready (and some of the time it will say in the MLS available May 01 or August 1, etc.).

At least a month and a half prior. If you look too soon, there is no guarantee that the apartment will still be available when you are ready to finally move. Have you found anything yet?