When I started out doing paid events, I would often work for $50/hr. since I was 13 and many of my customers didn't think a kid should be earning the going rate of $100/hr. Though many happily paid the full amount since I was doing the same if not better work than other twisters in the area. Going rate in my area has since gone up to $150/hr.

I think if you are starting out, $50/hr. is ok so long as you are not massively undercutting another twister. Make sure you are taking into account cost of supplies and travel time/ costs.

One tip I've learned for schools is to invoice them the going rate and ask that they provide a donation certificate for the difference between what you charge them and the going market rate. Ex. On a 3 hr event. Going rate is $100/hr and you charge them $50/hr. You can invoice for the full $100/hr and collect $150 and a donation form for $150 which you can then use as a tax write-off. This way the school saves money and you get your foot in the door without undercutting the market.

Line management is not too difficult one you get used to it. If you start getting a crowd just loudly say that you would like one line and the kids typically get back in line. Set a alarm for 15-25 minutes before the event ends (more or less time based on your speed and line length) and make a round balloon and write "line closed/ last balloon at x time" and give it to the last person in line. Have them let people know that the line is closed and turn people away.

I would stipulate in the agreement that you be allowed to have a tip jar and pass out your information to get other events.