Maybe I'd be responsible for something grossly negligent...like leaving my front door wide open while I wasn't home and someone walked in and stole it. 

Long-term, the national average real estate appreciation will probably be about 3% per year (2.5% inflation + 0.5% inflation-adjusted gains), but they can vary widely from place to place, and the place you expect to see gains might have losses, and vice versa.

I found that years ago trying to get a marble slab for my 5' wide vanity I couldn't get it below like $800. 

There are single wide trailers that are 1300 square feet.I have a 70 year old single male tenant renting a four bedroom house that is 2000 square feet.

The short answer is MHPs and self-storage have outperformed apartments over the last 10 years, and in the last 5 years, MHPs have outperformed apartments and self storage by a wide margin. 

Also, if you do need a new roof to go solar (if you have less than 7-10 years left on your roof) the 30% tax break will apply to the cost of the solar array AND the roof!

Purchase price: $1,900 Cash invested: $1,900 The trust purchased a 1968 Baron Single wide mobile home.

I live in the area :)   (technically,  upper rainier beach so a bit farther north just into seattle)Neighborhoods around here do vary widely as to their appeal, type of property most prevalent and the type of tenant they will attract. 

It comes in 15 ft wide rolls which means no seams and I just lay it down with no padding a quick staple and tuck job .

However: there are, of course, a wide range of legal regulations and tax implications.