Is it legal to buy and resell t shirts?

We want to start a small t shirt tye dye business but we don't know if we have to buy a certain brand of t shirts to do it. We wanted to use the Calvin klien t shirts but it is tag-less and the information is instead imprinted on the shirt. so, is it legal to buy these calvin klien (or any brand of t shirt for that matter) t shirts, change them, and resell them?