Wow! It seems like an awful lot of work. I am trying to visualize your project. When you say that you want to cover the TT with spray foam and then siding and new windows....is that directly onto the TT?
Having owned farms, I really doubt you will be able to rent an indoor space to live, as a barn. Insurance policies would not allow that. We were to remove batteries/gas if we stored anything in the barn, then you have propane also.
You have a lot to think about. I don't want to spoil your enthusiasm but I would think it might be both financially, physically and emotionally exhausting.
Good luck with whatever you do.
