I am looking at a 1998model Boxter with very low miles, less than 20k. The seller informs me that the oil has been changed but no other service. What do you think?

 

He should have done at least a 15k mile service, which is fairly basic. It includes air filter, pollen filter, oil change, and thorough inspection of the car. If it is a 98, that means it has been driven less than 2k miles a year, which can be bad for oil seals. Definitely get a pre purchase inspection done on the car by a qualified Porsche shop. Look for oil leaks specifically. Garage queens leak.