Nobody will understand your business as you do. This is a point that cannot be stressed enough. If you’ve never started a business before, I can assure you that the number of details and complexities will surpass your wildest expectations, and the only person that will understand your business like you do, when you need help the most, is a co-founder. This is why I have never started a business alone. My twin brother is often the first person I consider for this role; not because he’s family, but because his skills are complementary to mine, and he sees the world from a completely different perspective.
We all know that problems are going to come up while building a business. No need to beat a dead horse. The issue is that you’re going to need the perspective of another person that understands your business as you do, and that person can only be a co-founder. It’s equally as important that you have an opposing view, and I can count on my twin brother to challenge me when I’m wrong. Getting a co-founder that thinks as you do and shares the same opinion (all the time) won’t be much better than having no co-founder at all. Get someone who is equally skilled at what they do, but whose skills are complementary to yours and not the same, and most importantly, someone who thinks differently from you.