This is a topic that I am all too familiar with. I love making crocheted gift items, so I have tons and tons of them just sitting around. I often wanted to take them to craft fairs and little weekend "markets" around my home, but was always worried of getting into trouble.
Since I am not a very "seasoned" crocheter, I can not design my own patterns, I am very limited to what I can make and sell. Most every pattern that I purchase clearly states that they do not wish you to make and sell items using their patterns. I have found one person who was very willing to allow me to sell the items I make using her patterns, however, I can not sell copies of the patterns themselves. I am very gracious to her for this, so I am including a footnote on the card I attach to them stating who the pattern was designed by.
If we can not sell items we make following patterns that we purchase, how are we to become a productive craft shop? So far, the only way I have found is to contact each seller personally, asking them if they would allow you the rights to sell items made from their patterns if you give them proper credit. Some are willing to allow this under their guidelines, others are not willing to do that at all.
All the items in my shop as of yet are all my personal patterns, passed down from my family members who designed them. When I do upload items I made from another crocheter's patterns, I will make note of it in each items description. That way, they are still getting proper credit in return.
I am currently searching for more designers whom are willing to allow us this option. I would even be interested in maybe giving a portion of each sale to the original designer, if neccessary.
If you are crocheting for profit, please make yourself aware of the copyright laws on handmade crafts at www.creativecommons.org to avoid infringing on someone's original designs. It could save you some heartache later on.