Coinbase says that "the Coinbase vault has zero fees".
Uh oh. If they don't charge a fee, how do they make money?
The traditional Bitcoin wallet ways of making money were speculating with customer funds and stealing them.
Coinbase makes money by charging fees on exchanges to/from BTC/dollar. So you can store BTC in the vault for free. But they'll charge you a fee if you want to exchange them for dollars.
But...
Rule #1, never store your BTC in an online wallet. Move BTC in and out of online wallets for trading/exchanging only.
Rule #2, if you don't already know Rule #1, you shouldn't have anything to do with the world of crypto-currency.
Now as a Legendary member of this forum, I'm sure you already know these rules. But it's a warning for noobs.