Search for +required +deposits and you will find plenty of previous discussions:
1. This is not prohibited under the anti-tying rules;
2. You cannot require preauthorized transfers for payments see Reg E 205.10(e)
3. If you place a hold on the deposit account you have to provide the required deposit disclosure - 226.18(r) and its Commentary.
_________________________
The opinions expressed are mine and they are not to be taken as legal advice.