Sometimes that's easier for the poster
It depends on what type of printing you want to do (and how much you want to do yourself).
You can outsource the printing (heat press or screen printing or direct to garment) OR you can buy the materials and equipment to do it yourself.
Heat press is basically using a big heated machine to press a design from transfer paper onto a t-shirt. The design on the transfer paper can be printed on your home printer or even printed on transfer paper by a screen printer (plastisol transfers).
Screen printing is pressing ink through an actual "screen" directly onto a garment. This is the "traditional" way of printing t-shirts. Sometimes called silk screening.
An optical cutter can cut letters shapes, logos and all types of things:
http://www.t-shirtforums.com/showthread.php?t=5073