In any case, my question is this: How should I vet this person to 1) make sure he`s legit, 2) make sure I can trust him, and 3) make sure we`ll get along.
My other question is - how could (or should) a business arrangement be structured so that I maintain my interest in and control of the company without diluting our ownership too much while still making it worth his while?
In my years in business, I have partnered in many different ways with startups and with more established businesses. There are as many different ways to it as there are people in the world to the power of 20 (or more).
As far as your first questions go, the best way to do this is to get to know him, not to rush it. Just like when you chose to get married... how did you know you could trust her, that you would get along? You asked questions, listened to the answers, and listened to your gut.
I bet a few times in the dating process you were wrong. More often than not. It happens.
So, after that, minimize the risk. What are you willing to risk? Does this partnership require that you give him control of finances? Of your brand image? Of anything you cannot risk?
If so, can you limit that risk, bringing him in with minimal exposure for a trial before you open the doors completely?
As far as retaining ownership; has he asked for ownership? What about commission, since it is marketing, stating that % of growth from starting point forward would be his? Or a straight commission from sales, with no ownership, or ownership earned after a period of one year, increasing to full partnership within 5 years (if you are in for the long haul, he should be, too, and he will be willing to wait).
There are so many potential ways to do this. Really think it through. Talk it over with your wife. Then, talk it over with your potential partner. Ask lots of questions, rather than making lots of statements, and see where it goes.
I also suggest the book "Make Your Own Luck: 12 Practical Steps to Taking Smarter Risks in Business," by Eileen C. Shapiro and Howard H. Stevenson.
I borrowed it from my local library last weekend, and have found it very useful in clarifying risk/reward thinking.