I see that you relisted the question. Please feel free to ask follow-up questions. The more information you provide, the better.
The only way to truly protect an invention is with a patent. Without a patent you do run a risk by contracting with a service offering to assist you bringing a product to market. I see that you are asking about that option.
As to verifying the legitimacy of such a business
, there are steps you can take to reduce your risk. The first step is to attempt to deal with a local company with a local office. If you cannot find such a service locally make sure the business you are consider has a physical office in the United States and has been operating in that location for years. Ask for references from the company. If the company is a corporation
, which is likely, then go to the Secretary of State's Office web page in the state of registration for the company. You can search at that web page to determine if there is actually a company by that name registered to operate a business.
There will be a written contract involved. You should carefully review the contract and consider having an attorney reviewing the contract. You can have that work done for perhaps a few hundred dollars. You need to make sure you are not assigning ownership interest in the invention and that you are not waiving legal recourse in the event the company takes your idea. In your situation, without a patent, the most important step you can take is to carefully review any agreement you sign before giving the company information about your invention.
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Thank you so much