Are you currently self-managing or do you have a management company?

The area has certain advantages like shelter from regulation risk (pretty much as low as anywhere in the country if you buy in the approved STR tourist zones) and long term security (people aren't going to stop going to Orlando anytime soon). 

Do you recommend making relationship with property management companies?

It may sound nice to pay a 6% management fee but the extra fees can add up to be more than the other company that charges 10% with no additional fees.

I know that the general guidance is that emergency funds aren't to be invested, but given our financial security and the fact that we already have a personal e-fund in a safe, non-volatile location, would it still be crazy/unwise to invest this 15k in an S&P500 index fund in a brokerage? 

Loan Security: The property will serve as collateral for the seller-financed loan.

You just need a very savvy real estate agent, a  lawyer, a title company and a good relationship with the lender.

@Christopher Smith there are many...but in my opinion really only three companies out there that offer the ability to 721 into a large and diversified REIT that i'd feel comfortable with. 

So I did a 3-2-1 buydown and secured a 2.875% interest loan for the first year of the loan, and it will gradually go up a percent each year until it hits my rate of 5.875%!

Better if the company has a lot of info in writing that you can absorb to minimize this.