Normally speaking, top 15 or 20 schools can guarantee you loans without consigner (免担保,免抵押贷款) once they extend you an offer. That's why you can go to an expensive top MBA without a penny.
This is how it works: some commercial banks such as Citi Group has established program with these schools. Offer is the only pre-requisit.
Good point. The VO may challenge you that "how can you offset the loan if you come back to China to work (where remunition level is much lower that that in US)?"
That's why scholarship is so good. It pre-clears such kind of Q. And a tip is: even if you get full loan, you need to prepare a fund certificate for visa purpose.