The personal use days would only be if you are using the rental portion of the property for personal use (so that would be the rented RV space in this case). If you aren't using that space yourself during the year, then you have 0 personal use days. Land isn't depreciated, and so if they are just renting bare land, then you don't have any depreciation to report. Other costs like mortgage interest can be split in proportion to the part of the land that you are renting, as a fraction of the whole property. Utilities can be split using a reasonable method to determine what portion should be allocated to the renter vs. your personal use.
When you say "we share facilities in another building on the property", it depends on the specifics of that, but if there is a portion of the building that is exclusively for use by the renter, then that portion would be eligible for depreciation.
David Orr
Tax Modern
