I thought when you walked into a bank and deposited $$$ that it was supposed to post immediately?
Depends on the bank. Also, sometimes, on the customer and/or how late in the day it is. It probably could be immediate or at least pretty soon afterward - you can limp into a random convenience store at 3:30am on a Sunday morning, hand your PayPal debit card and some cash to the half-wasted cashier... and even that is usable within a half hour or less. Or so I have heard.