is this legal? Options

[Melissa]

someone suggested that i should sell my vectors and i actually think it's a pretty good idea; maybe not the vector file itself, but if i sell and ship out prints/posters of different sizes. i have no problem doing this with my illustrations, since they're completely original, but i was wondering what the laws are regarding things that are already copyrighted.

for example, if someone wanted to buy my ironman vector in poster form; is it illegal to sell something like that if it's based on something that really isn't mine to sell?