e38's are very expensive to fix, from the $3k for both cats when they go, to the $700 water cooled alternator, to the $1300 job to reseal your intake when the PCV goes. Dont forget the $1200 job to replace your rear upper arms and ball joints. And when electrical components go, good luck taking it to a gas station and gettimg them to figure out why ac control pannel has no display but the blower is blowing, and wont turn off.
My opisnon and many others would say stay away from the 7's. There huge money pits and a large majority of them are beat into the ground, expecially 2000's and below. 2001's are usually nice, since they all have the good options and its last year of production.