Mileage
18,000 miles and more indicates a need for a cam chain tensioner extension (Verslavy).
Same mileage tends to point to possible need of vac petcock tube replacement (or a replacement mechanical petcock if you swing that sorta way)
Tires, what shape are they in? Originals were IRC tires (and they tend to suck pretty much when they get half worn out or better). A 2003 should be on its second or third set of rear tires and second front tire unless it was a low mileage garage queen.
Ask who did the maintenance on the bike. Front pads, check them (you can see them if you look closely) for thickness. Ask about brand of oil filter used and brand and weight of oil that was used.
We can mention all these things, but you don't really know what we are talking about, really. But the fact you are asking will back off the price somewhat as the seller does know what we are asking about ....
Oh yeah, check the ildle speed -- if it isn't a fast idle then the bike may have been partially starved for oil in the upper end (cam bearings).
The seller is selling it for some reason -- at 18,000 miles we have a good idea of why.
Listen to the following videos before you go and be familiar with idle speeds and "cam chain slap sounds".
http://suzukisavage.com/cgi-bin/YaBB.pl?num=1308708632