[jasle]

Well, guess I have a different opinion. I used to live in Portland Oregon and had to commute almost two years on a bike in the rain about 300 days a year.
in general riding in the rain sucks. For the rider but also for the bike. You are much more likely to get surface rust on many places you would not think of when riding a lot in the rain.
I now live in Texas. I sometimes ride in the rain and find myself having to clean out the pockets of allen head bolts because they are starting to form rust in them.

So to me "never seen rain" means the rider is not hardcore committed to riding, bike probably only seen some Sunday cruises. This really has no impact on the mechanical condition because you still don't know if they maintained the bike well, washed it, etc...still need to do due diligence in checking the bike out.