I am looking for ways to supplement my income, and I've read that some modelers sell their models online. Is this a realistic way of making a little extra money for a relative beginner? I figure I'd be killing two birds with one stone by learning/practicing the software, and then selling the models.

Assuming your models are decent quality, how much money could you realistically expect to make this way? Where is the best place to sell models? And are there limits on the kinds of models you can sell (like are you allowed to sell a spaceship from star wars, or an object with a brand name on it like a coke can?)