I think you need to define "the right". Is it The copy rights for ownership? Clip art sites do not sell rights to own. They sell the rights (to use). Individual artist or agencies will sell the full and complete rights but it's far more expensive. If you want to do custom art, use clip art. If you want to create a product line of your own, use a freelance artist or create your own or hire an artist. If using a freelance artist (you must) spell out your intentions and desires for owning the art out right (for full and complete rights). Otherwise you won't own the art. Just paying a fee to create the art is paying for a service and does not give you ownership of the rights to the art.