Question about starting my own custom t-shirt business?

So I have been going back and forth thinking about this, and I am by no means a risk taker. I am a Graphic Designer, and have PLENTY of experience in e-commerce sales and marketing because of my current job. I was thinking about starting my own t-shirt website, possibly selling on ebay as well to get the ball rolling and coming up with designs for shirts, not silly ones with strange phrases but nicer things like you would find in the mall. Then selling them at the lowest possible price, for example if the t-shirt costs $5 and the screen printing costed $3 then maybe charging $10 for the shirt plus shipping which I think would be a fair price. However I don’t know how much the screen printing would be I know I would have to do it in bulk in order to make profit and keep the shirts affordable. How hard would it be to do the screen printing myself, Any feedback, warnings, ideas?