Breast milk ?

Tomorrow I will be 36 weeks pregnant. I'm curious to when my breast milk will come? I do plan on breast feeding for at least 6 months. How long also is good to breast I don't want to do for long because I don't want a 1 year old on my tit and I'm going back to work. Also I wake up and sometimes have crust on my tits and my it's only leak once of a clear liquid. Is it possible it won't come at all ? I really want to breast feed for my baby. I do have a doctors appointment Friday so some of my questions will be answered just wanted other mothers opinions