My T is 30 years older than me, older than both my parents, who had me when they were 26 and 23. There are some ways I connect with him that are very paternal and the age difference does facilitate that. But, there are some ways (like when discussing being in a band or other things we've both been actively involved in), where it can sometimes feel more peer-like. Because of that, I think I could probably work with a T that was a bit younger than me (though not too much younger, as they wouldn't have much experience in that case). From experience, I know I wouldn't get quite so much paternal transference with a younger T, but (also from experience in non-T relationships), I know they could still be very helpful to me and I could form a different "flavor" of attachment with them over time.

I can't imagine going anything more than five years younger than me, though. That would put someone in their late 20s, and younger than that would be, most likely, pretty recently out of school (which might be OK, but still, I hesitate, because I'm...complicated) or just without a lot of life experience to where I feel like my experiences would be easily understood. I'm not saying there is no one out there mature and intuitive enough to handle it...just that it might be a rare find for a good fit.