A bit of advice. Do check that you are not doing an internship with immature first time CEOs/CTOs.

I've seen an intern lied to, abused and dismissed without recommendation letter and promised salary by a CEO/primary founder of a YC company that I was with. This was no fault of that intern and AFAIK was done primarily because that [recently immigrated from India] CEO wanted to save about $3k of moneys. One of the reasons I've left that company and dropped from YC BTW...

edit: a clarification. this is anecdotal evidence and probably doesn't reflect statistics of YC companies in general.