I wish you the best. personally I would never buy a camera used. if the shutter goes (knock on wood) thats a few hundred dollars and you dont have warranty for that. I bought mine new with 3 years mack vip diamond warranty (an all risk type) and it costed $170. and the shutter will die. its just a matter of time. check it well and fingers crossed all checks out ok. dont want to be a debbie downer, Its just these cameras are sophisticated and any small thing costs so much.
I see where you're coming from, but understand that cameras are a lot more resilient than you think. I mean, when was the last time you heard of a camera like that having that sort of issue at 24k clicks? Especially from someone you know well? Especially a gear-head that you know well? Of course the shutter will die. Eventually. But the thing is, how many years of use will I get out if it? Three months or (more likely) three + years? My bet is on a camera of this caliber, 4+ years is about right, and even then there are D90's that are still going strong, far outliving their estimated lifespan on the shutter mechanism.
Granted, if I were buying say, a 3200 or similar I wouldn't be buying used
This just happened to fall into my lap from a good photographer friend who I trust and know well.