The best thing to do for longish term storage would be to hook up a small trickle charger to the 12v battery so that the electrical system and residual battery discharge don't kill the lead-acid battery. Even one of those small 5W solar panels would keep it topped off. Unfortunately modern cars always use a bit of electrical power when they are off so that the alarm and clock can stay on, but as long as you keep it topped off, or start it every month (or less) it should be fine. Starting it occasionally wouldn't hurt anyways because the high voltage battery could use a charge now and then. If you don't want to start it, probably getting the HV battery full before storage would be best so it can self discharge and still have plenty to start the car later. The cold won't hurt the battery, although they don't work as well in the cold they can be stored just fine.

If you get a Prius with VSC you'll probably
want to drive it in the winter.