Boulter,
Ok with the storage, but a word of warning, do not store the coach over open soil. Ask anybody you know that has looked at a "field car" the top may look great, but the bottom is GONE. This is because moisture transpires out of the soil and continuously collects on the metal. It's as worse that a 50 hr salt spray test.
Your value for maintenance is a little high for multi-year ownership. Tires are best amortized over there calendar life. (~8years)
You guess for first year depreciation I believe to be low. I have seen way higher values than that. It has been my experience that depreciation flattens after 5 years so I do agree with the right hand end.
I seldom see such a rational approach to RV ownership and this is
pleasant.
Then, over on a famous social website you can easily find writers that think living in RV will be cheap.....
Matt