Having been through the jointly owned PA minefield, I'd strongly advise that each band member buys/owns the constituent parts individually - one owns the mixer, one the tops and so on. That way if someone leaves, they take their item with them and no arguments about buying them out, value etc. At worse, if you split up and sell a complete PA to share out the proceeds, you can lose a lot of money. Been there, done that. Am fortunate in owning my own complete rig these days - decided to buy to avoid another loss. Gets me gigs, too. I'm a crap player, but people hire me for my kit