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.