Does the Avalon have a chipped key as part of the factory anti-theft system? If it does, such a system usually requires additional hardware and cost to allow the car to remote start and still retain the antitheft feature when needed.

I have had three remote starters installed on three vehicles, two of which have chipped keys. My advice: Unless you are damn good at installing electronic equipment in a car and have access to the wiring schematic/color codes for the Avalon, farm this job out to a pro. Be prepared to dig down a little deeper into your pocket.