More than half of my pipes are estate. Some arrive and are shipped off for a new stem. Others are so pristine that I just run a cleaner through them and load up. Lately, the better eBay sellers are dealing in very good clean pipes. As previously mentioned, alcohol on a cleaner and a good scrubbing of the airway and stem is a good idea though.
For those who are grossed out by who may have used the pipe previously - that's what enzymes and immune systems are for!
Anything on the stem short of mold will be long dead before you get the pipe in your mouth.