What do u mean with "broke"? Is this your main business? Most people (almost all I'd say) have model selling as a secondary job besides serious graphics work (they make models for commercial purposes and then sell them to make some more money) so it's not very common to go broke because of low sales (they are just a bonus to normal work anyway). But if this is your only activity, then you probably don't take it seriously enough and then you can't expect to earn much money from it. Make a website, start your own brand, make the models in better quality than the competition or do something that others don't do and you'll get your sale.
The more common things you do, the less sales you'll probably get.