I have one large cabin with a pool table, air hockey, and ping pong.  Not a lot of seating because it's packed with tables!  My interior decorator is revamping my game room and feels like we need to have a living area...

For a duplex, you don’t need anything heavy.If your main goal is income/expense tracking and clean reports, Stessa is popular and free — it’s built specifically for rental property financials and keeps things simple.If you also want rent collection and light tenant management, Innago, Avail, or TurboTenant are solid low-cost/free options.Since you’re already familiar with QBO, just avoid overcomplicating it.

However, I am still curious if there is any other popular method. 

The Tucson Market has a variety of Duplexes and I'm sure you can find one that is suitable for 12 month leasing and possibly Mid-term Rental, though for anything travel related I find that large one bedrooms are the most attractive ( I manage Furnished rentals as well as 12 month lease).To conservatively underwrite you would need to use the base rent of a 12 month lease up, no furnishings (much less popular in the old pueblo).What areas are you looking to Invest?

I came across a Triplex 5 miles from my home, 2 blocks from a good college, and basically across the street from an A+ popular highly sought out school district. 

Wholesaling is a common entry point for new investors.First understand, the guys on You Tube that are popular, state in their YouTube videos that they spend between $25,000 and $50,000 a MONTH to get the numbers they are talking about.

It is the most popular software in the industry, so your Tax Preparer will likely prefer it.

This is not a very popular area for STR at least on these boards, I'd recommend joining a local host group on Facebook, you will probably get much better feedback. 

It's also user-friendly and affordable, making it a popular choice for individual hosts or small teams.

I started with a basic template and added tabs for different unit counts over time.On the tech tool side, DealCheck is popular for quick multi-family screens.