I started investing in T-Bills back in the 80's.  At that time you had to invest $10,000 for one.  Now they start at $100.  The common ones are 13 week and 26 week.  There are also 4, 8, 17, and 52 week Bills. When I started I needed a car,  so I bought a 90 day T-bill which payed 16% interest and financed the car for 2%.  It was great ! 
Treasury bills can be bought directly from the government for as little as $100 by participating in one of its regular T-bill auctions. To do so, you must first set up a TreasuryDirect account and select the BuyDirect tab to choose the specific bill and amount to purchase.
Banks and institutions sell them also ....  Forget those places, when I started I checked the local bank fees, $25 to buy one and $25 for renewal.  You are getting hosed real bad.  Back then I bought with a 20 cent stamp from the federal Reserve Bank Detroit MI.  Now all purchases are electronic.  Just set up a Treasury Direct Account and you are good to go.
I buy 90 day T-bills and stagger them monthly so as they raise the interest rate you catch the rise every month somewhat.  This was August 14 auction price on 13 week bills.
Term:                         13-Week 
High Rate:                    5.295%
Investment Rate*:             5.456%
Price:                        $98.661542
You do not have to pay any State tax from the income on them and if you want to you can have a percentage deducted for tax if you wish.   I have one account set up at my financial place just for the income from T-Bills and to buy from.
Once you get started I am sure you will be happy.  If you do not have a renewal set up on your bill at expiration time it just flows back into your financial account.
Good luck
Ed
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Oh .....  I forgot to mention when you buy do the "Non-Competitive Bid"   .............  That's all !
Last edited by trapperEd; 08/26/23 01:09 PM. Reason: non-competitive bid