Dealing with Contreras: Isaac will need the player to bring back 100 pieces of scrap metal in order to manufacture the wares Contreras asks for; this can also be completed by using Speech 80 or Barter 80.
He lives in his house almost directly east of the Gun Runners' kiosk and across the street from the Hostetler home. Entering the house will result in Karma penalty, and he threatens you to leave. However, you can still initiate dialog with him after this.
On rare occasions, Isaac may be killed by randomly spawning Fiends that may appear in the area near the Gun Runners' factory, or nearby his house to the east (spawns at night).
Isaac is bald under his hat.
It's interesting to note that although he works and backs the Gun Runners, he is usually found wielding a one-handed plasma weapon, such as a plasma pistol.