Hi Harry,
I was reading this string and had a few comments of my own to add. First, I find that a typical patent search costs between $300-500 and does a pretty good job for determining whether there is something worth pursuing. You can tell from this preliminary search whether the differences between your invention and other patented inventions are sufficient to make yours patentable. You can read a lot about the considerations used in determining novelty and nonobviousness at the patent office (uspto) website. But to figure out how valuable your invention is (how different it is from the prior art in a commercially viable and successful manner), you may well need a patentability opinion which will cost another $1k-1.5k.
You don't need to file any kind of patent application to market your invention to businessmen or existing businesses in the hopes of licensing or selling it to them. But you should establish the invention date (by a detailed description and drawing dated and signed by the you as the inventor and perhaps even mailed to yourself). You should also use and NDA or confidentiality agreement whenever you talk to others about it. The risk you run by marketing your invention without filing an application is that someone else may independently have the idea and then file on it first. Also, you run the risk of it becoming publicly disclosed which begins a one year grace period, within which you should file a non-provisional application (even shorter periods in foreign countries)
Myself, I advise against filing a provisional patent application for two reason. First it has little benefit and probably none to a smart businessman. It does protect you from an independent filing as described above, but filing a provisional also starts the one year grace period. If you don't file a non-provisional within one year, then you and your businessman will lose the ability to seek protection in foreign countries. From my experience, I think it is hard to produce and market prototypes, negotiate and enter into a satisfactory agreement, and have the application prepared and filed all within one year.
Second, doing a search and filing a non-provisional application has important implications in a business relationship. Your businessman will want to know that the idea is protectable (in a commercially successful manner) before investing. He will likely think that if you haven't done the search or filing, then you are not confident and serious about it. Even if you are able to convince the businessman that the invention has great value, the question then becomes who should pay for and take the risk of the upfront costs? If you want him to pay for the patent process, then you will end up losing a lot of the value just to save the upfront costs (through an equity assignment or good deal terms). Thus, if you really believe the invention is valuable after having a search done, then you should perhaps begin the full patent process to give you more leverage in negotiating a business deal. And keep in mind that a serious investor can always pay for the upfront costs at a later date.
Anyway, I wish you good luck!
Nick Skarlatos
Law Office of Nicholas Skarlatos
(732) 560 - 5980
njslawoffice @ yahoo . com