I'm 20, will be 21 in April. Will also be applying for this summer's Y Combinator round as soon as I can get my prototype/alpha up and running for basic testing and as soon as I can find a founder. It is ridiculously hard to find a founder when you're surrounded by 9-5 types who have a family and a mortgage. I should've done this while I was in college. Hopefully I'll see some of you in Cambridge.