Who knows where Cloud stayed after Zack was killed. Cloud sure as hell doesn't. He probably just wandered around in an LSD-like daze until he finally made his way to Midgar, where he recovered his somewhat-functional senses enough to realize that he needed money, hence joining up with Barret and the gang.

One thing I just noticed:

Quote Originally Posted by TheAbominatrix
(SPOILER)Nibelheim did burn down, it was rebuilt by Shinra in order to keep things quiet and enable the Reunion.
(SPOILER)It was rebuilt just to keep things quiet. The Reunion didn't happen until years after Nibelheim was rebuilt.