Yes, this is done frequently with the 0% offers that CC companies send out. I've seen countless occasions where poeple get 100K of credit lines, and stash it away in a high yield savings account.
OK, wrong terminology, not a cash advance but a check written to yourself and put as cash in the bank yes, that works just fine
You will find that many equity brokers will not accept checks that are obvious sources of borrowed money. So don't try to write the credit card or home equity check directly to them. Put it in your bank account first.