The best business partner is somebody who likely wouldn’t be your friend outside of business. This may sound counterintuitive, but it’s important for business partners to compliment each other’s skill sets and personalities, not behave as clones of one another.
Friends tend to have similar personalities, perspectives, and interests, which can actually be counterproductive in a business partner setting. Ideally, your partners will have different skill sets than you, think and approach problems differently, have different levels of risk tolerance, and a high level of dedication to achieving your shared goal of success for the company. Diversity of thought around a common goal is arguably the most important part of a business partner relationship. Think about you and your partner as puzzle pieces that connect, each filling in gaps in skill, perspective, and experience the other might be lacking. If partners are too similar, it becomes very easy to get caught in positive-feedback loops, where a bad idea can get progressed down the pipeline due to the lack of a counter perspective.