When I was fresh out of college, several of my coworkers were 10-20 years older than I was, from totally different backgrounds, and they are still some of my closest friends. Granted, there may be some differences in life experiences between your average 20-something and your average 40-something (a few had children just a few years younger than me), or with people who have vastly different beliefs, but as long as you're open to the possibility and so are they, wonderful friendships can flourish. I think sometimes those friendships just come out of both people being in the right place at the right time and sharing a similar experience, whether that be work or school. Good luck in finding an awesome friend!