I've never hired a guide in North America and don't ever intend to but I have done so in Canada and Africa because the law requires it. In both Canada and Africa I have done 2x1 trips and they work well if the other hunter is someone you know and trust. In my case it was always my father. I had no problem letting him take the shot if he wanted and he had no trouble letting me take the shot if I wanted. The scenario isn't ideal for most hunts but for family members who get along it works well and it can cut a lot of $$$ off the tab.

As to tipping, I always budget 10-15% but I don't always give that much. There are a lot of variables that come into play.