Tax cite?

Anybody have a tax cite or IRS publication # for the proposition that mobile homes separately titled as personal property (true for park homes) are treated as real estate, not personal property, when leased as dwelling units? This means that for mobile homes:

  1. 27.5-year straight-line depreciation is mandatory

  2. rents are excluded from self-employment tax

  3. gains and losses are capital, not ordinary

Since mobile homes are personal property for state law purposes, the darn CPA wants to treat them as personal property for federal income tax purposes.