If you're part of the club scene, where everyones involved for the love of the sport, and as a favour to you they give you a tow rating then one could hardly expect payment.
I know I've had a lot of help into my career by others unpaid in various club scenes and I've returned the favour to the club(s) with quite a bit of my free time in return. Thats what clubs are about. I think most of them would fold if it was any other way.
If, on the other hand, you're towing for a professional outfit that engages for profit and you come along with a self funded qualification, then some sort of remuneration prolly isnt out of the question.
Up to you.