No, no, no, no, no...this is totally wrong.
Speaking from an investor's perspective, we like multiple co-founders (not just equity participants) for a number of reasons:
1) If I'm going to open my network, open my checkbook and open my operational expertise to you. . . I want to know that in the population of the entire earth, at least 2 people wake up every day and think 100% about how to make my contributions to you pay off for me (yes, it's all about me!).
2) I'm going to assume that you have strong skills in a particular area of expertise. And, what I'm looking for in a co-founder is that you've selected/found someone that has complimentary but opposite skills. Why isn't hiring for that a good idea at the start? It's the vision thing. Salaried employees weren't there at the start...they weren't there when you sat around and discovered the idea that you're now building into a company and if they were, then they should be co-founders.
3) One of my personal hangups is 'paid hitmen/women' who are brought in to a company and who trade some cash for equity...hate that! You know those people that will help you raise money for either a finder fee or equity stake; yeah, hate that model too. It's the same thing for me with founders/co-founders; you either believe to the depths of your being that this is the idea to pursue wholeheartedly, or, you don't. Co-founders have different motivations than equity holders and certainly different from salaried employees. I like it when I see companies who have people that are 'all in'. They've risked their own money, their friends and families money, their personal career trajectory and their personal lifestyle because they believe so much in what you are doing...those are the types of company that have a significantly statistical better chance of making it.
Good luck and hope this helps.