The 251 (essentially identical to the 253 in every way you care about) in my 03 TS has been going for a very long time with a bad driver-side head gasket. I would have pulled the motor and put MLS gaskets in by now but every time I think about refreshing the engine the Delta torque grind cams enter my mind and then it becomes a very expensive proposition that ends with me making stupid power.
In general, single slammer Subarus are anvils. Early DOHC cars are more trouble.
During normal operation: check the oil and coolant levels every couple of fillups and make sure they're good.
As for inspection/hammering the dealer on price:
Look for blow-by by removing the oil cap at idle - and if you see it, replace the PCV valve and clean the valve cover breather hoses after freaking out at the dealership how that means "bad piston rings" for a discount.
Note that many of the Saabaru body panels are becoming hard to find: this may impact insurance premiums if you choose to carry full coverage.
Fun fact, since you mentioned it: the Linear does not have a hood scoop. If this one does, I'd bet money that it was crashed and they chucked an Aero hood at it since that's all they could find.
If you do end up buying it, I would send it to an alignment shop to see if the caster numbers make sense or if the accident bent a control arm, which is very common for curb-involved accidents in Imprezas.
Other things I generally look for on Impreza wagons (boy have I bought a lot of these) include the removable rubber strips on the rear fenders (are they clean underneath? is the metal beneath rusted?), headlights that aren't the same level of 'worn' (again indicating a front end accident), cracked or missing timing cover, torn weatherstripping around the front windows (indicating failed theft attempt or leaks), loose or sagging front bumper covers, leaking or torn front CV boots, tires that aren't the same on all four corners.
It is really common for the passenger-side C-pillar trim to be 'popped out' a bit: the clip at the bottom gets strained over the years and lets go. You could probably use this as a negotiating lever but it depends how seedy this lot is and where they got the car from (auction?)
In my part of the world EVAP codes are very common: this is usually because the previous owners ignore the warning sticker inside the gas cap that tells you not to keep trying to fill the car up after the pump has already stopped. You see a lot of people who want to "round off" their purchase at the pump and just end up filling the charcoal canister with liquid gas. After a decade of this clownshoe idiocy, the charcoal falls apart and then things get bad for the rest of the EVAP system, which leads to me swearing at the previous owners for not being able to read a frickin' sticker. The vent valve wiring also sometimes becomes corroded from road salt and will throw codes when it shorts.
Good luck! I have been looking for a nice Saabaru for awhile to complete my descent into madness. Perhaps you will get there first.
