I've seen a couple of different types of investors who pay all cash.1.

I plan to live in the ADU and rent out the main house.

Please note -- although this is separate from property management, IF your PM handles this for you in addition to traditional property management, is the fee you would pay them for this different than if it were a completely independent construction manager/overseer not already associated with the apartment complex?

But South Florida has been my main focus.

We have our agent and lawyer selected but are between two different lenders.

You will find people have been successful in a ton of different ways. 

I've included an example below to help illustrate this.So different lenders have different rates (which do vary even for DSCR loans) but these are factors they all consider.See example below:DSCR < 1Principal + Interest = $1,700Taxes = $350, Insurance = $100, Association Dues = $50Total PITIA = $2200Rent = $2000DSCR = Rent/PITIA = 2000/2200 = 0.91Since the DSCR is 0.91, we know the expenses are greater than the income of the property.DSCR >1Principal + Interest = $1,500Taxes = $250, Insurance = $100, Association Dues = $25Total PITIA = $1875 Rent = $2300DSCR = Rent/PITIA = 2300/1875 = 1.23DSCR lenders generally let you vest either individually or as an LLC.

I work with mainly investor clients and pour over the MLS daily to shop these "propportunities" to my clients. 

My question is - if I wanted to take a loan out against that property to pay debt I owe in a different country and buy an investment property in a different country:1. would I be taxed on it? 

In my opinion, there are better locations for STR investments.I beg to differ with @Mike Lambert, I don't think the "ship has sailed in Tulum".