I need some starter ideas in engine repair?

alright so im taking this class in school to learn the basics and im pretty confident i can jump into this hobby. this is a pretty broad question but im looking for maybe a snowmobile to fix up, what kind of things should i be looking for? iv been looking at craigslist and there are endless offers for polaris indy's for good prices from anywhere 200-500$ but i really dont know the basics of snowmobiles.