From a practical viewpoint, as Daniel says, the fact that it's getting that far shows that the most failure-prone hardware systems are working.
That said, you cannot wipe the boot drive in a Mac, so either the drive could have been wiped from another one which was then removed, was removed, wiped and replaced, is defective, is just some random drive from another machine, or was carefully wiped by a caring, ethical person, gently replaced and just needs a fresh install.
So, you gotta ask yourself… Do I feel lucky?
Well…do ya punk?
There is very little difference between this and buying a used car. If you go into this expecting you may need to buy a new drive and/or other little things, you'll not be depressed when and if you do.