Before you buy let me tell you something, If a water damage or salvage title or rebuilt, repaired title doesn't scare then I would rather hold on it and fin one for the same price but with a lot less miles. I personally just bought mine for 5500 and its a 2007 legacy gt limited just like that one except no spoiler and it has si drive. It does have a water damage title but the owner gave me a folder full of receipts from where they basically replaced the whole engine at Subaru. And I bought from a private seller not dealer. But if you still want to go through with this then:
Ask for maintenance receipts especially for the new turbo. Look underneath the car for any signs of rust, bring a jack or ramps and check all underneath the engine for leaks and anything broken. Take your time with it and don't rush. Take it for a drive like a 30 min or more drive and make sure u feel the turbo boost and throw u to the back of your seat. Make sure all functions work( heated seats, sunroof) stuff like that. And the banjo bolt, I hear people talk that if you don't replace it it can really damage the turbo. Also make sure all the warning lights come on with one click. I've heard of many people ( not here) that take out the airbag or check engine light to sell a vehicle. I can go into more detail but I'm sure you get the idea. And trust me I buy cars all the time and I find good deal, so this one could be good and true! Good luck man hope to hear you join the lgt community with one.