Best Buy expects that the iPhone 5 will be available for pre-order during the first week of October. BGR points to an internal memo:

Thanks to a leaked document from a Best Buy source, we have discovered that Best Buy and Best Buy Mobile stores are anticipating taking preorders for the iPhone 5 starting in the first week of October. What’s a tad bit more interesting, however, is the mention (and further anticipation) that Sprint will be carrying the iPhone 5 at launch.

Of course, the dates may be changed. Noteworthy to say that the Wall Street Journal is also anticipating Sprint will be carrying the iPhone 5. Meanwhile, Best Buy is also expecting a new "Apple Fixture Installation" on Friday, October 21st.

To be clear, this isn’t a run-of-the-mill installation for the big box — our tipster tells us that the request that a manager be on-hand at 6AM is out of the ordinary (they usually show up at 7AM for inventory), and that a similar arrangement was scheduled for the iPhone 4 launch.