If patent costs are still beyond your budget, you have other choices. The U.S. Patent and Trademark Office (PTO) offers inventors two other ways to file and document the date of invention. Although these filings don't replace patents, they offer some legal protection. The first option is:
Disclosure document: You may file a disclosure document with the PTO that describes through words or drawings any aspects of your invention you wish to disclose. Each one-sided page must be numbered, any text or drawing must be able to be photocopied, photographs are acceptable, and no prototype may accompany the document. One original and one copy of the document must be signed by the inventor and sent with a self-addressed, stamped envelope and a check for $10 to Box DD, Assistant Commissioner of Patents, Washington, DC 20231. No one reads this document; the patent office simply keeps the original, stamps the copy with an identifying number and date of receipt and then returns it to you. Unless the disclosure document is referred to in a separate letter when you make your patent application, the document will be filed in the patent office for only two years and then destroyed.
Such a document does not initiate a patent application nor provide patent protection. It does, however, give you a legal document proving the approximate date of your invention. In the event someone then files a patent application for the same invention, you still must demonstrate an earlier invention date and prove you did not abandon the idea.