The Discovery is a nice, mid-priced coach. Used to be one of the most popular coaches, until other brands caught up with its features and price.
Check the age of the tires (date code on sidewall). An 03 likely has its original tires, which means they are due for replacement no later than 2010 and maybe due already (it is common for an early build 03 to have 2002 vintage tires). Tires in that size are expensive, so figure the replacement cost into the purchase decision.
We generally recommend that RV tires be replaced at no later than 7 years of age, regardless of tread wear. The risk of a catastrophic failure and damage to the coach is simply too great beyond that point.