Quoted from vid1900:

You are sadly misinformed and are ripe to be ripped off.
Federal regulations require that banks make check funds available within 48 hours.
But the actual check has not cleared yet.
When the check bounces 3 weeks later, your account gets the money the bank "advanced" to you subtracted and you get a $38 bounced check fee.
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That is how those fake Cashier's Checks and Money Order scams work on people like you:
You deposit the check.
A day or so latter the funds are "available".
You believe that "available" means the check has cleared (very incorrect), so you send the item.
3 weeks later the check actually bounces.
You get a chargeback from your bank for the full amount AND $38 for the bounced check.
You become another ripped off know-it-all; congratulations.