Commercial real estate appraiser checking in:
As has been mentioned already, typically the dirt is appraised as real property and the mobile home is appraised as personal property. The owner of the mobile home gets a tax bill based on the value of the trailer, and the owner of the land (if different) gets a tax bill for just the land, as well as any site improvements owned by that person (asphalt paving, for instance).
Exactly how the property (either the land or the mobile home) is appraised varies from state to state, and frequently from assessor to assessor. The primary variable for the mobile home is its size (typically measured from the outside walls), while naturally the land value is based on the size of the land. Either one of these is of course also based on local market values, or at least they ought to be (the quality of county assessors varies widely across the nation).
Pennsylvania may be what we call an “equalization” state. This means that if someone can show that the local assessor has valued a comparable property to yours less than he valued your property, you can protest the tax solely on the grounds that it is “unfair.” If reassessments are capped at a certain percentage over the last year, this can lead to a situation where the assessed value of the property has absolutely no bearing on the actual market value. This can give you instances where some homeowners have significantly lower property taxes than other property owners that are less “pro-active” in keeping their tax assessments low.
Another possibility is that personal property is taxed at a significantly higher rate than real property in your neck of the woods. In Oklahoma, it’s usually the opposite. Incidentally, a property tax of $1,800 in the Tulsa area would correspond with a market value of about $135,000 for real property (I don’t remember personal property rates or ratios off-hand, I rarely deal with that sort of thing).
What I can tell you is that, in a mobile home park, the owner of the park is paying a hefty amount in property taxes for just the park, without any consideration for the mobile homes unless the park owner owns them as well. It’s conceivable that the owner could charge a pro-rata share of the real property taxes back to the tenants, but I’ve never seen that before.
If you’d like, I can go into excrutiating detail as to the appraisal process for real property, and less so into the process for personal property.
Oh yeah, I should also point out that I have no experience appraising property in Pennsylvania. If you’re still really curious, rattle off an e-mail to your friendly neighborhood county assessor. Most of them are more than happy to answer any questions you’ve got regarding how they determine tax assessments. You also might do a Google search for your local assessor’s office; many of them have extensive websites with very informative FAQ’s.