Analysis paralysis, lol. Been there, it's a good trait but can stall you as you are experiencing. You don't need to know how to draw, but you do need some basic pc skills, and an eye for what might be attaractive to potential customers.
I did exactly what was already suggested. I copied and pasted a bunch of pictures into word to give a basic look to what my vision was. I emailed them to my cousin and her boyfriend who are graphic designers and bada boom. There you go. If you don't have a cousin who does graphic designing like I do, look locally on craigslist, junior college or universities and see if you can get someone to help.
Professional designers are not cheap because, well they're pros! But I bet you'll find a lot of people willing to help. Just as csaluone has offered up their assistance.
Back to analysis paralysis. I got the idea in Feb to do my own line, print my own shirts, and start an e-commerce site to sell them. I'm now two weeks into my site being live (and I don't even have my printer yet). My point is, take action and things will start to roll. ACTION makes the world go 'round.