The United States Patent and Trademark Office (USPTO) www.uspto.gov has a wealth of information on the patent process for inventors. They talk about the basics of patents and the process.
That being said, the actual process of writing the patent application is just the beginning. Once the application is submitted, there is a long process of responding to Office Actions from Patent Examiners (basically the examiner lists reasons why your invention may not be eligible for a patent and you must respond in turn) and can take several years. Then if you actually receive a patent in the end, you must monitor it and ensure that no one is infringing.
While there is software that could be used to write the patent application, a lawyer is most likely necessary to respond to the patent office. I would also say a good patent attorney is usually vital to write the best claims for your application - to have the proper language and broadest scope possible.
All in all, the patent process takes both time and money.