Wow,, 40k and no walls!! adding,, adding,, adding...... dang thats a lot of hours at work,, wouldnt see it for 5 years!

Parking a trailer for a week or 2 is legal,, as long as I move it off the property when I leave? Or if its on a cement pad or on footings? whats to stop from building on footings or a cement pad and throwing a couple big axles underneath,, as long as it can be moved? The camp we we used to stay at was built on footings,, and im pretty sure there was no papers involved in it.

Anyone have any thoughts on buying with another individual or a small group?

As soon as you involve the locals and the building authorities, its headaches from the get go. Consider this. What can or will they do if you go ahead and build on your lot? So you get fined for building w/o a permit. If you do decide to build, then build to local specs and building codes. As soon as you have inspectors involved, you are going to have delay after delay waiting for them to do their thing. Its certainly worth being charged with building w/o a permit than all the aggravation they can cause with all their petty delays. At least you'll have your camp finished on your time frame. Same thing if you put a 5th wheel or trailer of some sort. Do it and wait for them to tell you what they want. These guys will drive you nuts. The guy I hunt with near Evansville built his camp then added all their requirements for gray water and outhouses later.

As to the second part of your post regarding sharing the lot with a group of friends I would suggest you move real careful with that one. There can be all kinds of problems with that one but nothing insurmountable. Sharing of work load, maintenance of the camp, improvements to the camp and lot, when and how much the camp is used, replacement of propane and firewood and basic camp staples, and who and how many guests can be invited by each partner are all issues that can cause undue stress within the party. These must be resolved with nothing less than a legal and binding contract.
I just finished building a camp 24 x 32 and its large enough to comfortably sleep 8. Most of the lumber, insulation and plywood came from a portable at a school that we dismantled. So look around for these types of deals. Our camp on the island is 16 x 20 and really is just large enough for 4 guys. It can get really crowded with our guys and all the clothes and gear in hunting season. If you still need info drop me an email. I have a number of friends with a camp on the island, and I can get in touch with them if you need specific info.