Do you have to get specialized insurance? We have third party liability but would we need more than this? Would it be wise to get them to sign a waiver like when you go to a riding school?
I don't own a menage or anything but when I have taken ours to other places I have had to sign a waiver before going in the school or xc course so I would say it's probably a good idea
I would be avoiding taking cash for it, better to have some favour swap or something other than money, partly from insurance perspective (it may only cover you for private use which they may interpret as you and friends not paying people) and partly from planning perspective.
I spoke to several insurance companies today about public liability and they all have an add-on to the liability policy if you hire out your arena. Sorry but I didn't ask how much as we haven't built our arena yet and I only needed the livery part.