Here is a link to their fee schedule.
http://www.gmacbank.com/fee-schedule.do
Here are some specific fees with regards to balances.
Money Market Savings Account Monthly Services Charges
If the Average Daily Balance of your GMAC Bank money market savings account is GREATER than $500
NO MONTHLY SERVICE CHARGES ON YOUR ACCOUNT.
If, however, the Average Daily Balance of your GMAC Bank money market savings account is LESS than $500
The Monthly Service Charge for Direct Deposit Accounts will be $5.00 per statement cycle or
The Monthly Service Charge for NON-Direct Deposit Accounts will be $7.50 per statement cycle.