I would use these guide lines for a recovery period that I have found in the IRS publication 225 for farms. I'm aware you are not a farm but I believe the situation is similar to yours. I would not use the Vehicle Expense section. Instead, I would enter it under the Asset/Depreciation section. You can obtain this recovery period (7yr, 200/DB, HY) in the Rental Property (schedule E) by using the preselected asset category choices. When you are entering the motorhome in the Asset/Depreciation section select "Tools, Machinery, Equipment, Furniture" then "General Purpose Tools, Machinery and Equipment". This will give you 7yr, 200D/B, HY.
From IRS Publication 225, page 42;
https://www.irs.gov/pub/irs-pdf/p225.pdf
House trailers for farm laborers.
To depreciate a house trailer you supply as housing for those who work on your farm, use one of the following recovery periods if the house trailer is mobile (it has wheels and a history of movement).
A 7year recovery period under GDS.
A 10year recovery period under ADS.
However, if the house trailer is not mobile (its wheels have been removed and permanent utilities and pipes attached to it), use one of the following recovery periods.
A 20year recovery period under GDS.
A 25year recovery period under ADS.
