Same as with any other car really, service records, particularly fluid changes - oil, trans, ptu/rdu, coolant, etc. Then turbo-related stuff - is there pooling oil anywhere in the piping, are pipes cracked at the clamp areas, etc. Pull the pipes off the turbos to inspect the turbos closely for pooling oil, damage to the impellers, etc. Check struts and shocks for leaking fluid, tie rod ends, control arms and hubs for wear. If tires are worn, they will need to be replaced soon. Any codes stored in the PCM. If a P1000 is present, you should check again once the P1000 resolves. Hard to tell if the car is tuned or stock/ever been tuned. Check battery for CCAs. Suggest getting an AGM battery with high CCAs, toughmax 850 for example. Sunroof drains should flow freely. Sunshade should work properly.
Do not buy without having a warranty in hand, whether it is CPO, powertrain, etc. Electronics are expensive, and won't be covered by powertrain, so something to keep in mind.