If you (or anyone) can't affort to get a copyright or patent, here is a cheap little trick that can help if your worried about someone stealing your work.
If the subject is something you can put on a digital medium, or an idea you can write on paper,
mail it in a sealed envelope to yourself. Make sure the envelope is tightly sealed so no one can ever claim it's been opened!
mail it to yourself and keep it closed.
If you ever need to proof that the work is originally yours, in court for ex, the time stamp on the sealed envelope will make your case.
I've done this with my early poetry before putting it on the internet and they are still unopened.