So if I was able to get money into my coinbase account after waiting however many days it takes I would be able to buy bitcoin right away and have that bitcoin that day?
Nope. You don't get fiat into your coinbase account. You link your coinbase account to your bank account. Then when you buy
BTC you're locking in the price of the
BTC you purchased, but it takes a few days for the
BTC to show up at coinbase. They give you an estimated time for the coins to show up which thus far has been 100% accurate for me(100ish transactions).