You have got a very good response and advice already as above.
A few cents from my end, as I am in similar shoes.
Working as a partner or co-founder is a long-term commitment, and both (or more) should have same passion and commitment to reach the common goal.
I would be more inclined to chose a long-known friend who understands me well with similar understanding, passion and interest. But it is not possible in all cases.
Since you are the primary founder of the business and you are inviting another to come aboard as a helping hand to build and grow (with same passion and commitment), you better should know what exactly you are expecting from your (prospective) co-founder for building the business.
As advised above, dont be hasty and dont talk too much about your business idea or whole complete business plan in the first date itself. I would rather start with a nice friendly chat discussing his goals, past experiences and how his expertise could help my business. Even if my business idea is part of the conversion, I would not disclose the whole idea or business plan in complete details, rather I would try to know more about his expertise, his industry experience, how suitable it is to my line of business, his experience of how he had/would approach a VC or Angel for investment, etc.
He should also be able to understand your business idea and his honest feedback on it. Because, without understanding your business idea or technical proposal (ie, your brainchild), he would not be able to present the idea well to any VC or angel for raising a strong financial help.
Importantly, as a partner or cofounder, how far he could go with you in up and down phases of the business and his commitment for his mutual/financial help to shape up the business as you planned.
If all go well with this preliminary phase and you find him is a very good fit to your interests and objectives, then go for an advisory board for further steps.
I would like to know how it went and whats the outcome of the blind date. May be a good-to-know lesson for me too. Please update.
All the best.