Piston Slap...had it on my 02 WRX wagon.
When cold and been running for 30secs lightly and gently stroke the throttle from inside the car...doors shut, radio off, windows up. Sounds almost like a very lightly knocking cam but you'll know what it is when you hear it. When it's properly hot, do the same again and the noise should have gone. That's the best indicator of pistonslap. If it's still there when hot, definately walk away!!
I wouldn't bother with it if it's got piston slap as eventually it will need a bottom end rebuild. Been bitten once already although it lasted 40K miles before bigend failure, but was getting progressively worse as time went by. I'm sure that contributed to botton end failure which largely was due to oil starvation from a sticky valve in the oil pump.
.....and make sure it's had a new Cambelt and FSH.
If you get a good one it will last forever as to be honest there's not a lot goes wrong with a WRX as none of the engine or drivetrain components are really heavily stressed with 215bhp, and i have to say my suspension was very good when i got mine with 47K miles, and it still is!!
I prefer the way a wagon drives and handles compared to the 4-dr. Doesn't skip around so much on rutted B-Roads and seems to hold the road better.
Good luck with it :thumb:
P.S. An MY02 WRX with 50K miles and FSH should be