There really is no one-size-fits-all answer here.

Next, lenders don't want to make loans on projects of that size (nevermind the class), so you are probably in for all cash. 

In your opinion what are the Pros and Cons compared to more affordable multi-family properties (besides the initial investment size)?

Depending on the size of the cut they are either a little motivated (1-5%), moderately motivated (6-9%) or seriously motivated (10% or more). 

In other words, you need to do your own market research and find out what other new units with similar size and amenities are renting for.  

2 unit homes also have larger conventional and FHA loan size caps then 1 unit homes do, so you have more wiggle room to borrow more.  

It was parked in the driveway of an STR, so the two properties could hold a medium sized group (more beds, wifi, 2 baths, 2 kitchens).

Fast forward two years - I am now in multifamily full time, buying properties from 200-500 units in size. 

Size makes a big difference on whether or not an LLC is needed.

I would first check my loan terms and verify if you have any type of pre payment penalty (which you most likely will).I would then do a side by side comparison chart with your expenses if you were to 1. refi out of the ARM and pay penalties+closing costs on new loan for a period of 5 years with your new interest rate VS. 2. keep loan as is and pay your current rate for the next 5 years and the refi at that point with that year's current penalty.Hope this helps and good luck!