I would pause on your quest for a successful t-shirt line until you organize your finances better. I help dozens of people a month locally get their design line off the ground, and the #1 reason I tell people to wait is: finances.
Can you cut back on spending somewhere? Turn off Cable TV, downgrade your phone service, eat out less, drink/smoke less? Can you earn more somehow? Get a second job, take odd jobs, etc?
Not having money to pay for artists is going to crush you. The reason I say this is because the good artists are BUSY with people paying them today AND paying them residuals tomorrow. You're going to the same people and saying "I can't pay you today, but maybe we can make money tomorrow." I'll be honest: you won't find good artists this way.
I work on spec because I run my own websites where I sell my designs. Therefore, I am working for myself. I take all the risk, but I get all the reward. No way would I give a design to someone else when I can sell it myself. Most good artists would do the same thing -- why give you the art if they can sell it online themselves and take the same risk but make more money?
Most people think the t-shirt game is about making money easily. Well, it is. I make 6 figures a year on my designs, and I'll be honest: I am a terrible designer with horrifying designs. The thing is, I had to pay thousands of dollars a month in the beginning to market my designs, to give out freebies to random followers on Twitter or Facebook, and to offer my designs to retail stores to sell (I gave each store 12 free shirts, to keep or sell or whatever, with no reimbursement to me unless they reordered).
Can you make money by starting with $0? Of course you can. But you have a better chance of success by investing some of your "skin in the game"!