I always recommend a qualified instructor. And personally, I find it a bad idea to use a friend. My friends were climbing, and one didn't really look out for the other because he had no clue what he was doing, and the other one got hurt. It wasn't serious (the injury) but the friendship is very damaged.
Wow that isn't any fun. Why is the friendship damaged, I'm sure that it was a big accident. I'm sure it wasn't on purpose or anything like that was it?
Sometimes people don't take it that way. When thinsg like that happen, their expectations from the other person is so much higher that when something bad happens. it kills the relationship.