Walmart cashes payroll checks for a $3 fee. You can load a Visa card there. Money orders are less than $3. If for some reason you can’t get a bank account, Walmart is affordable. In many Walmarts there are second chance type banks, too. They are for people who have unpaid fees and charges at regular banks.
USPS is just more gov’t tracking your money.
there are a lot more post office locations than Walmarts.
My concern is security. Post Office employees can steal activated Visa cards, this would become a big issue.