To refine what Neo said, not all private student loans defer payment. It depends on the terms you agree to.
If you defer payments and interest, expect a very high interest rate.
If you defer only payments, expect a mid-range interest rate.
If you choose not to defer--which isn't a big deal; as a minumum payment on such a loan will be like $25 a month--you will be a crazy low interest rate.
Also, make sure it's a fixed rate.