Like I have a friend back then, we always compete with each other but when every I need someone for assistance I go to him and vise versa. Because or competition is a healthy one.That is a very nice answer. It depends on the kind of relationship that both is building. If there's a hate relationship, then why should you make your rival a business partner. It's better to just mind your own business. If there's a goodness in the relationship you can partner with him or her.