Do you need to be an accredited investor to invest?
Do you take funding from the public through A+ for any YC startups?
Is it possible to invest in YC itself?
Not yet but that would be interesting to offer some day.
Please please please do this. I have invested in over 100 YC companies but my only way to do so has been FundersClub, Angel.co, and WeFunder. I love those guys but I would rather invest directly through YC. I am giving 20% to them for no good reason (other than access).