I did walk through it and saw the repairs needed, but its only a single wide trailer. 

Does anyone know of any nation wide lenders?

Opinions on this will vary widely so I'm just throwing out best guestimates but 25% of the GP split or 1-3% of the loan amount if an upfront fee which your investors would ultimately fund through their investments. 

This can vary widely by location, @Anthony Mikolich, but $10k looks ridiculously high.

Don't want to discourage you but you need to go in with your eyes wide open.

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.