I've done it with credit card payments on vacation rentals, won every time, and the money was returned to me.I will bet this is a tenant with a lower credit score.

My sister owns 17 SFH as well as an expensive personal residence in a different nearby town.

So you could get a DSCR Loan.However most DSCR loan I know want to see at least 20% down, but you might be able to find a lower lender or you would need to get a hard money loan and season it for 60 days and then close with the lender. 

The interest rate we would pay them would be more that the CD rate (win) yet lower than the banks mortgage rate (win).

The appreciation in this area is already booming as it is the top two most expensive counties in the state.

2-4 units typically have lower loan to value then do single family homes.

Income was categorized in expenses and expenses in income.

I've found Colorado to be one of the most expensive in the US, maybe followed by Park City/Deer Valley, Utah.

If you need to add those systems they can be incredibly expensive and time consuming to install, especially if you have to deal with current tenants. 

Personally, I like the all-in-one units but they are expensive and poorly suited for larger units where it will take forever to get a load of laundry done (since you can't move the clothes from the washer to the dryer).