In order to qualify for the Pay As You Earn Plan all your loans have to be Direct Loans (among other criteria)
In order to qualify for the IBR your loans can be Direct Loans or FFELP loans (if you meet everything else)
So the question is if I have both Direct Loans and FFELP loans do I have to just go with IBR or can I put some of my loans on PAYE?
The answer is often times yes.
As long as you meet the date requirements (no loans before 10/1/07 and one Direct loan after 10/1/11) any Direct Loans are eligible for PAYE. This will not affect your other loans as while you cannot have some of your Direct or FFELP loans on different payment plans you can put all your Direct Loans on one plan while all your FFELP loans are on another.
That means your FFELP loans can be on IBR while your Direct are on PAYE.
Another solution? If you consolidate your loans you will make them all Direct Loans thus making them all eligible for PAYE. Just make sure the dates work out!
This not only works for the IBR/PAYE but if for example you have enough FFELP debt to go extended but not enough Direct Loan Debit you can do an Extended Plan on one but not the other. The key is just to make sure all your loans on a particular type have the same plan.