For single-color you don't have to have a "machine." You can use hinge clamps to mount your screen to a work surface / T-shirt board. The shirt slips over the board so it is inside the shirt, and pallet adhesive holds the shirt in place while printing, else it would stick to the ink in the screen and lift up when the screen was raised between strokes. I printed my first shirts that way. Easy enough to setup if you have a few DIY skills and tools, or there are kits with the basic setup. An example, not a recommendation: https://www.amazon.com/Speedball-4513-Hinge-Screen-Printing/dp/B001E0FI3E
The other option is one of the real cheap low-quality one-station 4-color presses. These are a real pain in the behind to use for actual multi-color prints (as it is difficult to get all the screen registered with each other and to keep them that way), but can work okay for single-color. Again, just an example: https://www.amazon.com/dp/B071SL3JLG/
Besides that, you need screens, emulsion, scoop coater, warm dark dry ventilated place to dry screens, a way to get a dark UV opaque image of your art on a transparent medium, a UV light source (the sun can work, but exposure time will be harder to figure out), ink (probably water based rather than Plastisol), a way to flash your ink (heat gun or hair dryer, probably), a way to cure your ink (assuming you don't have a heat press, you might manage with an iron, at least to try things out, but better with something that can heat the whole image area at once like the larger Circut Easypress 2).
See the link in my sig when it comes time to figure out how long your exposure should be. The learning curve is steep to get to the point of having an image on screen that is good enough to print. Steep and frustrating. Many people give up here. The link in my sig greatly improves your odds of success.
As you can see, there a lot of options for a simple setup. My suggestion would be to watch a ton of videos relating to 1 color screen printing, and get some hinge clamps, do not buy an actual press, it's not necessary, and too much money. Now, if you're not particularly handy, then maybe buy a 1 color press off eBay, but definitely do your homework, good luck.
Maybe you can find a local screen printing supply business. They sometimes have basic used stuff for cheap and can help you with the products you need and or don't need. It's still probably a good idea to reference places like this because I've already heard of supply shops providing more than what's needed to move some product out of their door.
For beginner use i'll suggest these VEVOR screen printing machine which is great to use a home screen printing machine.
This screen printing machine featuring four colors and four stations. Full metal structure. 2” thick frame available under 300.
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