3 x Camera Concert shoot, But what equipment?

Until you get a budget, we're not really in a position to give sensible advice – we could go for a true teeny-weeny budget solution, with 3 random old camcorders, and ex-ebay mixer and some cheapo streaming software with skype like image quality – or we could spec some Sony 1500s, where the camera cables would cost more than the other system!

We need at least a guide budget – and if it's too low, people will suggest renting in the kit, rather than waste your money. Seriously though, a portable production unit with all the kit, like cabling and comms is going to be expensive. I've had a couple over the years, and tried to shave a few pounds off with some second hand kit – but the tiny things soon mount up. So how many thousands are we talking? New or second hand, and worse still don't forget to factor in proper flight cases – the best investment you will ever make!

Make certain your producer is CLEAR on his/her expectations.  Do they want a Tricaster, to swap views, make titles, etc.?

You are absolutely correct that you'll want to test out the equipment.  Perhaps you can tag along with another local production outfit?