How much do families fit in the with culture of startup? Would it be odd for an employee to have to leave in the middle of the day to pick up sick kids at school? Will you be a "good fit" if sometimes your family responsibilities trump work. What is your desire and inner motivation at 50? It's probably a lot different than the 20yr and 30yr old startup culture. I would say if you are 50 yr old that fits in with the younger culture and have the necessary skills you will do just fine. The reality is though that you are probably at a much different place than the majority of startup employees. You have probably see enough to know how to best spend your time and your priorities are likely different than your peers. The guy doing the hiring knows all of this and where he won't directly use age as a factor in hiring he will take these other factors into consideration. good luck.