I'm going to be contrary to the other respondents (that almost never happens ).
I'm a volunteer instructor at my club, one of two. There's a lot to go wrong with new model, especially when it has been built and trimmed by a newbie. I'm willing to assist with getting a new model/pilot through his first flights, and I'll give it a good ground check. Some things I can't see though - like the ARF wing joined with a thin smear of 5-min epoxy on wing halves that didn't get joined until 10 min later....... I always tell the owner of the plane that it remains his responsibility, and I accept no more responsibility for it than he has paid for. If that isn't satisfactory to him, he has the option of finding the other instructor.

Abe