My bigger question is why do you want to bring in a co-founder? Admittingly I didn't read every response here, but bringing in a co-founder entails lots of specifics and has a ton of good, but also a lot of baggage (not all baggage is bad, it is just there).
Are you trying to get external financing? Are you expecting to apply to an accelerator? Do you just not have the cash so giving equity is easier right now? Are you wanting to break up the load? How does employee #1 differ from co-founder in your mind?
My 2 cents. MBA's are fine degree's (and people usually), but in a startup I generally avoid anyone with an MBA unless they have been in industry for quite a while (5-10 years and at multiple companies). And as an early employee or co-founder an MBA is a red flag to me unless that person was part of the original team.
Honestly he sounds more like employee #1, but if you are looking for a co-founder to help offset the load you can absolutely bring him in as a co-founder. Just remember if the company is already legally formed there are a lot of little details you'll have to go through on the stock issuance/vesting/taxes etc -- e.g. get an attorney & CPA to help you.
Also, if you just need sales help that is much cheaper and easier to find than going down this path. If he isn't interested in sales you really should figure this part out. That said, co-founders have to do jobs that they wouldn't normally do until companies grow, so it isn't the end of the world. But in the case of sales, it is literally the lifeblood of the company, so it is pretty critical.
My last point. A Co-founder is essentially someone you will spend more time with than a spouse for the next 10 years. You will literally be seeing and talking to this person daily for hours everyday (at least in most situations). You are essentially married to this person, and they will call you at crazy hours and you them and you'll be under stress together and separate which means you have to support each other. If you have any questions as to this person get them out and into the open and make sure they do the same before you sign any agreements. If they smack their lips when they eat and that bugs you, get it out now cause when you are stressed and pissed and on the fourth meal of the day for the third straight day you'll eventually blow (I know stupid example but hopefully you get the idea). Personally, I'd rather keep a friend and not have a co-founder than think I got both and than lose them both in a year.