Negotiating MBA Associate Offer

I'd be careful. Thought process from the employer and your future co-workers could be "wow, this person just broke into the industry, and his/her initial thought is to negotiate"

It likely costs you more political capital than its worth.

Lol no, you're a commoditized employee that'll be worse than good 2nd / 3rd year analysts that are far cheaper than you are.

Some banks offer 2nd year fellowships, JPM comes to mind.

Pretty much no room to negotiate. The only negotiation I heard of (apparently from 3+ years ago) that was successful was was a guy moving to a different bank full-time after the summer internship on how long you have to stay so that you don't return the signing bonus (new bank offer had 2 years, his summer return offer had 1 year). His new bank also gave those same conditions to everyone else that signed in his class

From what I've heard of 2nd year fellowships, they are very rare and are given primarily (exclusively?) to diversity candidates, so depending on you situation that may or may not apply. If you kill it all summer and they really want you back, maybe you can ask about it when they give you a return offer. However, you will be less competent than a good analyst when you show up, and IB salaries are basically highest for people post-MBA, so there's not gonna be much sympathy on the bank's part for your ability to pay back loans.

With that being said, your question is vague as to whether you're asking about negotiating your summer offer or your A0 offer at the end of the summer. Obviously no one would commit to funding your second year of school before seeing your summer performance.