While it's speculative, if you're comfortable with a 35%-40% down payment, refinance and pull most of your equity out if rates come down in the following years—a strategy implemented time and again by experienced investors.

My final question is that you said you are turning a profit, but with all cash that is confusing as you have no mortgage payment. 

Keep in mind HELOCs are interest only payments, adjustable rates, and will eventually turn into a fully amortized loan (usually after 3-10 years).Cash Out Refinances are great when you need the cash for long term needs or consolidating debt.

Trust the process.Did you work with any real estate professionals (agents, lenders, etc.) that you'd recommend to others?

I'm willing to travel to Miami once or twice a year and manage the properties from Spain, hiring a good property manager to address issues, find new tenants, manage payments, and clean the property for new tenants.

This could temporarily reduce or pause your mortgage payments, providing significant relief.

You will have your original mortgage payment, and you will also have a payment on the HELOC if you have drawn from it.

How much (%) down payment would I need as a first time home buyer? 

Additionally, the owner's offer to share a copy of his passport, intended as a gesture of transparency, inadvertently contributed to our apprehensions.Given the paramount importance I place on maintaining the trust and security of my client relationships, I chose to err on the side of caution in this instance.

I will need some build out time approx. 30-60 days and would like to have rent reduced or make no payments until the renovations are completed.