This is a good topic to discuss with your business attorney but it is also relevant for a CPA to raise the point. We work with lots of small businesses and their owners. We've seen many partnerships work great and we've seen others that have ended badly. Well written partnership agreements are like insurance- worth their weight in gold when they are needed. What can go wrong in partnership? Partners can have different visions, short-term vs. long-term vision, a partner could develop an alcohol or drug problem, or a partner could die to name a few. This isn't a real uplifting list but the fact of the matter is that they do happen..
Without a probably agreed upon and exercised partnership agreement you have no way to know how things will play out. So take the time and money to develop an ironclad agreement. If things go bad on your end your partner will be protected and if your partner loses their focus, etc you will be protected as well.