I've also used traditional loans through regional banks and a few SBA loans. 

If you go into Central or South Scottsdale (Old Town) $1M will buy you a smaller, older home, OR half of a big, remodeled home (as alot of the Arcadia and Old Town area are turning over old small homes to be big beautiful homes in the $2.5M range and higher).There are options.....for both buying and renting, that would work with your situation.By the way....it's 51 degrees in North Scottsdale right now where I live. 

I know that interest on the acquisition loan can be included in the cost basis since it’s inventory.

Your personal loan has a 5 year balloon period.  

I can only imagine that they got a bunch of big time investors and business loans to grow this out.

Business loans typically won't let you purchase a property if you read the fine print.

Quote from @Ogonna Odo:  Small ones will not, they typically like cash or checks.

One thing I continue to think about is how valuable 2-4 unit properties are becoming, and will continue to be, since Fannie/Freddie took the income restrictions from the 5% down conventional loan option for house hackers. 

I am an aspiring serial house hacker based in southern New Hampshire actively searching for my second small multifamily deal in the Nashua area, but I've hit a wall with inventory being so tight in my local market.

If they have a good interest rate it might be worth looking to see if you could assume their loan to take advantage of the lower rate.