The car is in fact a Scenic 1 phase 2 and not a Scenic 2,it's just a facelifted Scenic 1 with a new nose and a general update around the mechanicals.
Make sure the cambelt has been changed,this can be both expensive to replace and expensive to put right the damage if the belt breaks.
Common problems include...
Water ingress through various places into the interior.
Window regulators failing.
Broken rear shock absorbers.(these arw difficult to spot visually,they will cause a knocking noise on a road test and the rear of the car will bounce all over the shop).
If it's automatic,be very,very carefull as the boxes are very troublesome.
Some Scenics seem to corrode around the rear arch/sill area.
Check the rear lower brace on the rear axle for corrosion.
I'm sure Scenic owners will add further thoughts too.