Eddie is right. I've marshalled for 10 years and competed in 4 Manx Grand Prix so I'v eseen it from both sides. It can be very rewarding. You will get the best training, support of everyone around you, meet friends every 12 months and feel like it was only yesterday, and have the eternal gratitude of the riders for allowing them (ok us) to do the most exciting thing possible on a motorbike. But please be aware that it can also be the worst experience you have ever had and YOU have to deal with it as a professional. In that time between the dust settling and the helicopter arriving, there is no plan B, no phone a friend. Good luck.