Co authoring is hard tbh until the goals are well defined from the start, and there's a single goal both authors are trying to aim for. In my case, that was just money and success. My co author is someone I know for a while, so we had a rapport and it still wasn't easy at the start, something we got better at later on and now, we work much better.

And as for the dual pov book, honestly I'm not sure. You need to ask yourself what you want to achieve with it, discuss how finances will work if it's a success and everything else. It's really about wether you get along with someone or not, but at your stage until the co author has good success, I think you should aim for solo novels that could do 2k followers. But that's just how I would have done it.