Speedball makes a kit, but it is only good for getting your feet wet. I used mine for one job and threw it all away. You will learn very quickly what all it takes to print T-Shirts.
It is a great business to get into, but don't let your artistic desires overwhelm your business sense.
I recommend you visit with various screen printing suppliers. You can find used equipment, like a single color press, spot dryer and a simple exposure unit that some small shop has outgrown and build from there.
By the way, I started my business saying the exact same thing you stated in your question. I sold a car I had to get started and everything worked out OK. I am an artist first, business man second.
I assume quality direct digital printing is "Heat transfers"?
If that is the case silk screening will stand up over time much better. But in silk screening it will cost an arm and a leg to do it full color, where as heat transfers do an amazing job with photo reproduction. I have been doing both for a very long time and will give you a few pointers for heat transferring images.
1) Use HP. Even though they are the most expensive I am sitting here wearing one right now that is 10 years old. To test the theory go to your local Staples or Office depot and buy a pack for around $24.
2) You can use an iron to press the image to the shirt but I prefer a proper heat press.
3) You need a good ink jet printer for this. Many seem to think Epson rules for best Ink jet quality...they don't (IMO). I really like the new Cannon Ink Jet Printers, like the PIXMA i4300. It is cheap and amazing quality.
Silk screening- Good but expensive with smaller runs. More environmental waste with this process. Larger runs, say 100+ this is most cost efficient.
Photo transfers- Great for small runs and photo reproduction. Proper washing and drying is needed to prolong the life of the image...e.g. drying inside out.