Ask HN: Founders' expectations

YC's W15 application deadline is Oct 14. What do founders, who have already applied or who are planning to apply soon, expect to gain from YC W15 program ? Money, Network and Mentorship are often sighted as primary reasons to join such program but which one is the most important among these three ? Are there any other expectations ?

I am not affiliated with YC or any other accelerator/incubator programs.