Our instincts are to eventually rent it and use the income for payment assistance on a new home mortgage.

I have enough down payment and can get a DSCR for the 4 plex, but would not be able to swing the other, even by itself. 

The main issue I have is contemplating the baloon payment at the end of the 2nd year and refinancing the remainder with a bank...how can I compute that into calculating the IRR?

I have 3 accounts per property which helps me leverage APY on savings accounts, prevent funds from being comingled, and easily set up auto payments for things like mortgage payments and utilities. 

If you tried to use the app to look at photos of your ads or look at the "charges" for rent payments and such it was pretty much unreadable and would have several glitches making things overlay on top of each other and such. 

Keep in mind of the I/O(payments/period) and game plan on how fast you'd like to pay it down. 

1099, social security, trust payments, annuities, etc?

By the time I reach 20% equity (likely 3+ years away), my monthly mortgage payment will come down when I refinance, but $600 is a big hit to the numbers. 

The carrying costs are low, but tenant was making partial payments by month 2.

You could front the down payment as well as monthly payments to the seller, then charge interest on them.