We've seen quite a lot this year here in MI. Mostly at class A resorts where you could purchase a lot just like in Florida. Some of the lots were very nice. Lot prices starting at $70,000 and up, and there was probably another $20,000 - 30,000 in landscaping done afterward. Quite a lot Prevost and upper end MH's. Rental rates were about $68 per night for someone's developed lot. Very nice setup.
There is one in Petosky MI, Hearthside Grove
http://www.hearthsidegrove.com. It's over $90 per night rental. Almost every other MH there is a Prevost or similar. I bet there would be some very interesting people you could bump into at that place.
Many at these resorts were full timers and part timers leaving the warmer states for something cooler in the summer. They hit the road around October here and head back down to the warmth.