I'm sure it depends on what curriculum you choose. I don't live in Missouri, but as far as I know I don't think any states charge to homeschool - I don't think that would be legal. Some states are more strict than others about requirements for homeschoolers though. There is probably some kind of independent support group in Missouri you could contact. If you can't find that, you might try doing a Google search for the Homeschool Legal Defense Fund. They should have information about your state or who you could contact with your questions.
I homeschool in Missouri and it doesn't cost anything but the cost of materials.