You need an intellectual property lawyer to advise you. If you really lack the funds for a patent, then there are some steps you can take that will provide you with some protections. Obviously, documenting with evidence sufficient to prove that you are in fact the inventor, and what it is you invented, and the date of the invention, will be necessary, as will having a well-drafted nondisclosure/noncompete and indemnity agreement before you ever communicate with any future or prospective buyers/partners, will be a few of the necessary things you will need. If the invention is worth anything, it will be more than worthwhile the fees you pay to a lawyer to advise you in these circumstances.
If by "software invention idea" you mean that you wrote a computer program then the code you wrote is protected by a copyright and you should register that copyright. Speak with a copyright attorney about how to do that properly [some of the code in the deposit copy of the work can be redacted if that portion is a trade secret]. Registering a copyright is inexpensive.
If by "software invention idea" you mean that you only have an idea for a piece of software then you're out of luck. There is no body of law that protects ideas -- as ideas. What you can protect, with help from your own attorney, is your disclosure of your idea to someone who can make it work in exchange for that person's promise not to use your idea if he chooses not to try to make it work. Your attorney will write a non-disclosure agreement that you will need to have the idea-recipient sign BEFORE you disclose your idea. This approach, however, is very often a fools errand because few serious idea-recipients will sign the non-disclosure agreement.
You should read the book linked-to below and then visit with your own intellectual property attorney. Good luck.
The above is general information ONLY and is not legal advice, does not form an attorney-client relationship, and should NOT be relied upon to take or refrain from taking any action. I am not your attorney. You should seek the advice of competent counsel before taking any action related to your inquiry.
You will have an extremely hard time selling the idea, try selling the invention.
If the invention is based on software, then you could register the copyright.
You need to consult a Patent Attorney and discuss the details. How do you know your invention is original? have you run a clearance? obtained a patentability opinion?
There are many questions you need to answer even before you think of a potential client.
USPTO Registered Patent Attorney, Master of Intellectual Property law, MBA I am neither your attorney, nor my answers or comments in AVVO.com create an attorney-client relationship with you. You may accept or disregard my free advice in AVVO.com at your own risk. I am a Patent Attorney, admitted to the USPTO and to the Florida Bar.
Without knowing more details it is impossible to advise you.
I will say, it is much more difficult to get a patent on software than it was a few years ago. If your invention is the application of an algorithm to a task, and the only novel thing is that the algorithm is being performed by a computer instead of a human, you will nto get a patent.
Copyright does not protect ideas, just the expression of ideas, so if you software is not complete you cannot get a copyright on it.
You should discuss everything with an IP attorney in your area.
Our intellectual property laws do not protect mere ideas. We protect tangible, useful inventions, or works of art, music, or authorship. Further, recent decision of the U.S. Supreme Court and Federal Circuit all into question whether patent protection can be obtained for most software "ideas". If your idea involves merely using software in a manner to sort, organize and/or explain data (i.e., a mathematical algorithm) or as a method for doing business or performing practical professional tasks (such as medical diagnosis or analysis of stock prices), you probably won't get a patent on it. Many believe that the best protection for software is copyright---and copyright protection is much less expensive. Case law on claims of copyright infringement is rather sparse, but in my view copyright often is more powerful than patent protection in this area.
Frankly, the world of technology moves so fast that most IP rights (patents, copyrights) are outdated by the time they are obtained. Your main concerns should not be getting a patent or copyright---it should be the following; (a) can your software invention be practiced without violating IP rights of third parties, and (b) can I find a business partner to help me develop and commercialize this software invention. You need to deal with step (a), which we call a clearance analysis, before you will find anyone willing to provide the financing and support necessary to develop your idea. A clearance analysis requires retention of legal counsel. Indeed, in the final analysis, the first step for anyone in your situation is to retain legal counsel to help guide you through the clearance and commercialization process. In this regard, you should avoid the non-lawyer get-rich-quick sites that offer to help inventors at low cost. Unfortunately, these are mostly rip-off artists. You need to work with legitimate IP counsel. If you do not have a budget for counsel, then your first priority should be getting this budget. This is why so many successful inventors start out by using crowd-funding sources such as Kickstarter. It takes seed money to make something like this happen, but there are many possibilities for raising such money (and a good IP lawyer will guide you toward those possibilities). Good luck!
Patents protect ideas, copyrights protect the expression of an idea. You have not specified whether your idea is actually embodied in software (i.e., you have actually written and compiled source code for a working prototype) or just an idea for a process that will be implemented in software.
Ideas embodied in software can be protected by trade secret, to the extent (a) the ideas are not of a nature that they can be observed through use of the software and (b) the software licensing terms prohibit licensees from reverse engineering, decompiling and disassembling the software to expose those ideas. Naturally, if the plan of your "buyer" would be to utilize open source licensed under GPL and even LGPL licensing terms, you could not impose such restrictions or rely on trade secret protection.
If you are forced to go the trade secret route, at a minimum you would need to execute a confidentiality agreement with whomever you approach to "sell" your idea. The problem you are likely to face is that most prospective buyers will not sign a non-disclosure agreement (NDA) (also called a confidentiality agreement) without knowing what problem your invention solves. Revealing that information before an NDA is signed, however, is often enough to telegraph your idea(s) - leaving you without any protection at all. Other parties won't talk to you at all unless you have a patent filed.
s protect any kind of information (including ideas) so long as they are not generally known to the public, adequate steps are taken to preserve secrecy, and