Why don't you get the shirts made yourself and sell them and keep more of the money?
Check out 10ShirtsFor99.com
They do FULL COLOR printing on the front, back, sides and sleeves with NO SCREEN CHARGE.
They have lots of options and upgrades. Including an option for 1 shirt. There is even an option to get the 1 shirt free.
They also do single shirt drop-shipping at
Well, screen printing is a specialist process that requires precise materials. Are you sure you want to do that anyway? With screen printing, you can only handle one colour at a time. You need to separate your image into different colours and prepare a separate screen for each colour you'll use and then print each on separately and align them with previous layers. It's tricky.
A simple alternative is iron-on transfers. You can buy printer paper these days which does the job. You just prepare the image on your computer print in through the printer onto the special paper and then iron it onto the t-shirt. The image won't last as long as with a screen printing process (50 washes or so compared to hundreds), but you can print in full colour without having to do any colour separation.
It's just about possible to do screen printing with home made materials (eg net curtains instead of a silk screen), but it'll take you quite a while to put together a frame and you'll still need specialist materials like the dye, screen mask and fixative. I'd suggest you go down the iron-on route.
Here's an example of such paper. It's pretty cheap.