Initially I started this project together with a friend. I am responsible for the technical part whereas he is doing the product. Now that we have MVP ready and looking for validation, market fit, and paying clients, it became obvious that none of us knows how to communicate, market, and sell it.
I joined https://www.startupschool.org to learn more about the non-technical tricks of running a company, and seem to be going the right direction (potential customer interviews, lots of them), but I have just 24h a day to split myself between writing articles in the blog, answering Quora questions, adding new features, and talking to clients. And so a third person joined as a co-founder.
He is a friend and a previous colleague of my company partner, I haven't known him before. I know that choosing the right partner is tough, and when money is involved things might get nasty, however after meeting him several times, discussing his experience, and writing down the agreement, I am quite happy now. He'll be helping with marketing and sales, exactly the skills we lack now.
If you're looking for legal templates, here's a good resource (EU): https://startupestonia.ee/resources