Being Payed to Do Lantern Repairs

At one of the stores I haunt, the owner is setting me up to repair a lantern for friend of hers.   She already told him I would probably want to be paid $15-plus parts before even talking to me.

He is going to need a new generator put on and what sounds like a basic cleaning.

Here is my problem.  If something goes south, I am afraid I may be held liable.  Second, one of the best ways to kill a hobby, is to get paid for it.

Her intentions are good, she thinks I can pick up some quick cash.  She has the ability, because of the type of store she has, to send me some work.  Please tell me what you think.