The reality is, this should have been discussed and agreed upon ahead of time, before having him do any work. Mixing friendship and business can be tough.
If he will not give you an amount, it may be because he is unsure of what you are expecting as far as a discounted rate due to your friendship.
If this is a cash deal, you could give him the full $80 per hour. This way, you do not insult him by giving him an amount far less that his skilled help is worth. This puts the ball in his court. He may really need the money due to work being slow, but not want to jeopardize your friendship over it by asking for the full amount. On the other side, he may feel the amount is too much and give you some of the money back. Either way, you got the benefit of having a skilled tradesman do the work. Better it be someone you know as opposed to hiring it out an being overcharged or nickel and dimed by some unknown contractor.
Another thought is, If you are paying him cash and the income will not be reported, then the going rate less taxes & overhead may be fair. Offer him $50-60 per hour and see how he responds.
