Every county has their own rates too, just like their enforcement of purchase price. If they try to jack it up you can try to argue that the additional value is the “business value.” Some people even spell this value out in their purchase agreements as land value + improvement versus goodwill.
I suggest that you call the Assessor and ask. They probably have a value placed on the land (which is pretty static) and a possibly a value on the infrastructure. The value of both may change periodically based on sales of like properties or some other metric that the county uses. Like jhutson mentions, list the value of each (land and improvements + goodwill (the amount you are paying over the land and improvement value) in your contract or have the seller sign an Allocation of Value document. The total should equal the purchase price of the park.
A good rule of thumb is to underwrite the deal as if the taxes would be increasing to the purchase price . This may be realistic , or unrealistic , but the assumption has merit and should be utilized. I have periodically seen a broker go to 80% of PP and they may be what the industry uses, I’m not sure.
In my area (Eastern Washington), when we bought a community several years ago, the assessed value was raised to the purchase price, so the taxes almost doubled the following year. According to a local attorney experienced in such matters, the county assessors can require park owners to provide financial statements so the property can be assessed using business income to estimate market value! If you decline to provide financial data, they can use their own methods to estimate market value, which becomes the assessed value.