What will your role in the business be, and what do you expect mine to be?
The co-CEO game can be difficult, so consider putting one person in charge.
How will we split up ownership, how will we divide profits and losses, and how will we each be paid?
Some experts suggest avoiding a 50-50 ownership split. But if you are equal partners, be careful about giving ownership to an employee--it effectively gives the employee the swing vote in any partners' dispute.
How are we going to make decisions?
What are your values?
Yes, it sounds touchy-feely, but there are important issues to be discussed: Will you outsource? Will you employ illegal immigrants?
How do you like to communicate?
What kind of hours are you planning to keep?
What's your spending style--and what's your credit rating?
Remember, lenders are likely to check the credit history of both business partners.
Where do you want this business to be in five, 10, and 20 years?
Make sure you're aligned on growth plans (including hiring, regional expansion, and so forth) and possible exit strategies.
Can I have references?
You have to know the partner's personality and business reputation. Check with vendors, check with Google, meet the spouse, meet the family, meet the friends. Go on nonbusiness outings. In other words, date before you commit.