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Need to change cash to cashier's check without bank account (Just arrived to the US)
A cashier's check costs money to get and is not connected to an account.  You have cash.  You should be able to get a bank to sell you one, even without an account.  Find a bank where you would like to open an account and explain the situation.  I can't guarantee that that will work, but I would expect it to do so.  If not, the bank can probably suggest an alternative.   You might also ask the landlord if you can do it with postal money orders.  I am positive that you can buy those with cash.  You might have to buy a bunch to reach your desired amount.  Or perhaps a Western Union money order might be better.   You also might be able to open an account with your passport and Social Security Number (SSN).