My question is around the mechanics of changing the insurance.

For a property with relatively new mechanicals/roof somewhere in the 6 months of mortgage ballpark is a good place to start for a vacancy/repair budget.

What is the average rent growth and expense percentage per year for Mobile Home Parks?

There are a lot of things to look out for like utilities, infrastructure, foundation, structural integrity, mechanicals, permit fees, contingencies, interest reserves etc.I would be happy to discuss more offline.

I received a lead on a mobile home and the seller wants out from under it.

Depending on the age of the buildings, there could be significant structural, mechanical and electrical problems that could easily chew through a combined 3K per unit budget.  

I have a mobile demo company, that I am bringing to the Tampa, Winter haven, Lakeland area. 

My assumption was that the property was a multifamily property (a mobile home park as that was where the post was) and that property was the owner of the treatment plant.

That's the advantage of being a renter - mobility.

Go for mechanical machines, if you can find them, that are easy to repair.