My friend stopped using heroin today to start a new job in 7 days. will he be done having withdrawal symptoms by then?

A lot of it will be: The worst symptoms of heroin withdrawal are pretty much better by 4-5 days, but some symptoms - sleeplessness, anxiety, leg kicking and cramps - may persist for weeks. Of greater concern is craving. My experience with people who have serious heroin habits is that very, very few (<5%) can get off and stay off without help. I strongly encourage 12-step or other support meetings & professional help.