The thing I am not sure is, he wants me to cover the permanent thing that will stay with property after he move out.

It means I'm non-us citizen nor permanent resident, so I can't open business account with bank like Citi, BOA etc.  

However, I confirmed that "traditional" financing on the prefabs is challenging, especially if not on a permanent foundation (which was an option in this case).

The pads are permanent, the homes can be moved, although unlikely in most cases. 

Traditional loans are unavailable to foreigners unless they have long-term permanent residency in country.

It is a permanent feature of life from now on.

Look for a bank who will convert the commercial construction loan into permanent financing.

Suddenly, buying your permanent house with one rental under your belt becomes plausible because you have a job, some rental income, and you might have thousands of dollars of equity from that first property. 

It also states that if they get the approval, the improvements that they make become my property once they are permanently affixed to the dwelling.

Or would you sell them at some point and buy a bunch when you get settle on a permanent location?