The first thing I recommend is to get the new book from the National OHV Conservation Council (NOHVCC) called OHV Park Manual, See it here:
This book has a ton of information on starting your own OHV park. It covers insurance, liability, some trail design ideas, and how to get things off the ground.
Next, send me an email with your idea, and I'll forward your email to my contacts in your area that you should get linked up with and see what they can do to help with local strategies and such.
And finally, read the stuff on my web site about the Recreational Trails Program grant money that you might be able to get (no guarantee, but it's worth looking at).