not necessarily
i print my own shit for my company, and it works out fine
if you know what you're doing, then its pretty much the same process that any professional company uses, just dumbed down a bit
and it lets you use more creativity and change things how you want them
for example, i print on home made tie dye t's, and other painted t shirts, which you can't get done from most companies
and i use AA for my stock, because the cotton's awesome, the price is awesome, and the shirts fit awesome, instead of some crappy shirt most online printers offer
yedig?
to the op, go to any art supply store and ask about their screen printing stuff
you need a 110 mesh screen, something to hold it in place, ink, squeegies and emulsion and some other stuff thats kinda needed but not really
you just gotta be careful