IF you happen to find an artist requiring no deposit — all you are gambling is the Time. Why gamble? Ask for samples of printed shirts if the artist is at your Printer's business; if a freelance, ask if they have a website to see samples of their work. If it's a freelance artist, ask if they can actually draw, and if they can do the art in a format your printer needs — for many artists have no such ability.
Finally, discuss your concept with them; if they start arguing for a concept THEY have, beware — it could be a sampling of what's ahead. MANY artists are fanatics over THEIR ideas and art — and don't really pay much attention to YOURS. They feel they should be worshiped since they can draw. A good rapport is crucial to working together in making your concept a reality!