To address your specific question, free consulting all by itself probably isn't a realistic option unless you know someone in the business and he or she is willing to give you free time. However, a number of service providers and marketing agencies include "free" consulting and advice as a part of using their tools, technologies and other services.
If you're not planning to spend much money on the website itself or the marketing after you launch, you're probably going to have to settle for online resources such as blogs, FAQ pages and customer support services included in your website provider's suite of services. If you do have a decent budget for building and marketing your website, ask your prospective technology and marketing providers to show you how they can help you with a strategy and plan to go along with their tools and technologies.
The second part of your question is a great reason to start a relationship with a qualified attorney. If your idea is worth stealing, it's worth protecting with professional legal counsel. Find an attorney with experience in e-commerce, intellectual property, copyright law, privacy, online security, trade laws, tax laws and all other Internet legal matters. You might have to find a firm with several attorneys you can work with depending on the issue at hand.
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