As an envoy, how long should I wait for players to show up before I decide to cancel the event? Due to some unfortunate circumstances (got my drivers license suspended, LONG story) I can't hang out at my local shop as long as I used to.

I usually try to wait at least 15 minutes. Though I suppose it really depends on how on-time your players and events have been in the past.

This is covered in the Approved Play document under Tardy or Absent Players. They have until the end of the first round to show so effectively an hour.

So you should start at the time you set with the people you have. If more people show up it is covered in the Approved Play document under Tardy or Absent Players.