After two and a half years, it is a bit of stretch to bring someone in and call them a co-founder! You already have a successful business, so you may claim full credit for that.

What you are really asking is how much should you build out your management team. On that score, you must. If you are pretty much the sole person running the show, then the first thing an investor will ask is: What will happen to my investment if you get run over by a truck? Crap happens, and if you are no longer running the show, who will take over?

If you don't have a person, no one will want to invest. So you should develop a management team that will be able to seamlessly take over should you not be able to continue. It doesn't matter what title you give these people, just make sure you have them.

The second aspect you need to address is growth and scalability. Sure you are doing fine now, but what will it take to increase revenues by 5X or 10X? If you don't have a team in place that can achieve that, then you need to get them.

No one wants to invest in a company unless it is scalable. That is how they achieve a high ROI within a few years. You need a plan to show that you can scale, and that you have the team in place that can do it. Again, it doesn't matter if they are advisors, or VPs, or whatever. The point is that you have to have these people committed to working to achieve that scalability.

If you can't afford to bring them on now, then that's a good reason to raise funds. But at least have those people identified and ready to join.