On the other hand... once you become familiar enough with your gear and with the halls/wherevers you'll be working in, you could find that the audio recording part of the task is: setting levels during the rehearsal (which most often happens in the hours preceding the show) and then hitting "record" before it all starts. I think this is called the "capture." Later in the studio you'll slave over the mixing process to massage the tracks into the final, beauteous, finished product. Placing the mikes where they oughta be (obviously before the soundcheck) is not a cookie-cutter procedure, to be sure, but again, once you've established a reliable protocol or two, it becomes kinda automatic.
So, I found myself, during concerts, just sitting at the rack of gear, listening and noting the times when pieces started and stopped. I didn't dare change any levels or anything, unless it was some kind of emergency, because chasing those changes, in the mixing, is nightmarish.
Which means that actually you can start the audio recording, and then move to your camera, and then you really need one person on each camera (aside from the overall static stage shot that can happen unattended) in order to follow the action and catch those touching/emotional moments that touch people so emotionally and make for an entrancing, compelling viewing experience. Crucially, the clarity and immediacy and overall soothing/exciting quality of the audio really does cement the whole viewing "adventure."
Charging a flat rate for the audio, and another flat rate for the video, which includes the time for all the editing, makes it easy for the customers to budget your involvement.
It cannot be overstated at all: the trust that your customers feel having you as a part of their artistic endeavors? That is the only thing that matters. Which means you need some kind of track record and word-of-mouth going on... and building that from the ground up takes time.