I like your strategy on using your primary HELOC to purchase a rental. Ok this is close to the strategy I will use in my flip process. Paying cash for the 1st rental is key and it is great you have the equity from your primary to do this.
So I spoke with one lender that deals with investment financing and this is the method.
1: buy house with cash
2: remodel and improve with intention of buying into equity
3: (this is the tricky part with time) Wait 6 months (some make u wait 12mo) and get reappraised with intention of financing for 70% the appraised equity.
4: Use the 70% pulled from 1st home to buy your 2nd property.
This method works better in flips because once the 1st home is sold you can do the method over agian. Kind of leap frog method. You always have one home in the works as one is sold.
As for lenders in Florida. I will be using VanDyk Mortgage. They will lend up to 10 notes. Give me a Private message and I can give you my contact person I speak with directly.
I hope this helps you and good luck