Does your co-founder have to be the same age as you?
jacquesm: I think what is more important than age is that your motivation for doing a startup is more or less similar.This is usually easier to find in your own age-group, but it doesn't have to be.Suppose you have a guy that 40, two kids, one in high school and a guy in his early 20's working together, you'll potentially get friction because both will have a completely different attitude towards the work (not saying in all case, but likely).Whereas both would be in a roughly similar situation that would make it easier to understand the others point of view and such friction would be less likely to occur.I've worked with people in a 20-50 age bracket and I found that it was sometimes very hard to explain to the older people that the younger ones were pulling their weight even though they weren't in the office at 9am, and to the younger ones that the older ones were pulling their weight even though they left at 5 pm... And that doesn't go in to issues like pulling rank because of age and so on.It depends very much on the people involved. It is certainly possible to have a large 'age-gap' but it is not going to make things easier for the most part, especially not if the younger person is actually senior in the business over the older one.