I understand why 2yr was mentioned since it easier to justify as an investment. 

The process of building a model yourself also is a good exercise in understanding what the mechanics of a deal are and allows you to customize your own process.Once you understand the process then using a more advanced model makes a lot of sense.

I FULLY UNDERSTAND THAT NO ONE HAS A CRYSTAL BALL AND CAN KNOW WHAT CAN OR WILL HAPPEN IN THE FUTURE.

I am now looking beyond my backyard eager to diversify my single-family portfolio.

Still owner occupied (current living here), but eager to get into my next property.

Looking to gain an understanding on (1) whether or not over/under units typically sell at less than side/side units and by what approximate percent less, and (2) is it smart to estimate less rent for units without a garage/covered parking?

So yes South Florida is a little weird, just need to work with an agent and lender who understand and can make it happen.Hope this helps!

Definitely agree with 1st set your goal by understanding your why then start executing on tactical goals to make the overall objective work.

I understand that this is an ambitious plan, but what would the rehab cost me, roughly?

You could buy a $10K program with all the bells and whistles, but if you cannot interpret the various metrics, and understand how they might apply to your particular business model then you will set yourself up for failure.