If you are already cutting vinyl I would just recommend doing t-shirt vinyl to break into the t-shirt market it has some limitations but so does sublimation.
You will have a much lower cost of entry (basically just a heat press) you can start to gauge what customers really want out of the t-shirts... lights vs. darks / cotton vs. polyester, etc.
Sublimation equipment and consumables can get costly and actually give you tons of headaches if you are not running it every day...
Just do a ton of research and don't believe any of the sales people or companies selling the equipment, all they want to do is sell you as much as they can or that you are willing to spend. They don't know your market or clients or how to run a business (in almost all cases).
Just my 2 cents.. and its worth just what you paid for it.
