01 owner here, bought it new when my son was 2, it's currently at 151,800mi.

He's 17 now and learned how to drive on the X5. It's a great learner vehicle. I can't speak to the 4.4i engine, as my experience is with the 3.0i. Plan on control arms and ball joints at a minimum and budget maybe $150-$200/month to cover "planned obsolescence" breakage items - like window regulators and it should run a long time. My daughter turns 16 in a few months and she'll learn to drive with it too.

You wont find much on the market for what your X is currently worth and it's a far better/safer vehicle that a 10yr old Civic.

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12 E70 3.5i xDrive
03 E46 330i ZHP
01 E53 3.0i
98 E36 323is
12 Audi A4 Quattro
79 Triumph Spitfire
73 MGB