Man, I've enjoyed the unique vibe (and the modern changes too btw) of the Mission district for 20 years, and I never thought it would become so desireable and precious this fast!

If they are modern (ish) double glazed, then you might be able to stretch that 2t unit and just shove another duct in.Also, find out if your power company offer any incentives for upgrading a central a/c system.

My greatest long term goal is to be in a position to buy historical properties and read them to their original splendor with modern conveniences.

Since the park doesn't own any homes it's not an issue, but should you need to bring in homes at a later date you want to make sure you can get a modern single or double wide house on the lots.There's a bunch of other stuff in regard to buying a park but this will get you started.

It has fuses instead of a modern electrical box. 

After listening to experts, the criteria a new investor looks for in a "first flip" house would be: Entry Level home with relatively standard design (cape, ranch, split, colonial as opposed to Modern or Unique) 3 Bedroom 1+ bath (I'd prefer 2 myself) in a neighborhood that has recently demonstrated positive activity where multiple sales are occurring with relatively short "days on market". 

Debt is modern day slavery - without question.

Btw, your website is very cool and modern@Leo B.

It wasn't cool exactly, and in the modern age I guess you couldn't say weird anymore either.  

A modern, direct-vented, condensing hot-water heater will have an annual fuel utilization efficiency (AFUE) rating  >90.