Most cars are suitable year round, provided it is set up correctly for the winter.
AE86 is a fun car to drive. But remember, it is nearing it's 20th birthday. Tonnes of aftermarket parts available, lots of used parts available in the junk yards.
Engine is nearly bulletproof, if well maintained.
Pick up a Toyota Factory Service Manual, and you may even be able to troubleshoot the majority of the problems yourself.
But a 15+ year old car, you should EXPECT many parts failing. So be ready to spend money fixing everything else.
But if you are looking for a beater, you'd probably not care about the rust. As the AE86 and rust go hand in hand.
Cheers,
Crzy Joe