T-Bills can be purchased from a bank, stockbroker or directly from the government’s Electronic Services for Treasury Bills, Notes and Bond service. Purchasing a T-Bill directly from the government will save you from paying commission; however you will be assessed a $34 fee if you sell before the maturity date. And if your holdings are larger then $100,000 you’ll be charged a $25 annual fee.
Also, when purchasing directly from the government, you won’t have access to the shorter 4 week term. You’ll need to visit a bank or stockbroker to purchase this type of T-Bill. Also, ask your broker about 182-day t-bills, which are popular investments.