It's not a 2003, completely different graphics scheme:
http://bikepedia.com/QuickBike/BikeSpecs.aspx?Year=2003&Brand=Cannondale&Model=R400+Triple&Type=bike
It looks older to me. (I'm almost positive that's a quill stem). My guess it's a mid to late 90's model.
Regardless it is way overpriced. It would be way overpriced if it was a 2003, and it's way way overpriced if it's a 90's era bike. It had low level components on it in it's day, and now they are a decade (or more) old. Price new (a decade ago) was roughly $800 (basing that on the 2003 R400 in the link above).
It's worth $100-$300 now depending on it's condition and your market.
If it fits well and it's near immaculate (ie it's sat in the garage all this time and just needs some oil/grease and a good tune) then it's a nice enough bike for what you are describing. If it's been ridden I would expect the drivetrain to be needing some work/new parts.
Regardless he needs to cut his price in half (if it's immaculate, and more if it needs work/parts).
I think you can find better on a $500 budget, keep your eyes peeled.