How did you find this deal and how did you negotiate it?

For curtain rods, charge him replacement costs; for curtains, go to a thrift store and see if you can find some that work and charge him depreciated value. 

Hi David,Yes, you can refinance into a conventional loan during the 5-year term if interest rates drop, provided your seller financing agreement allows for early payoff without penalties.

Anyone know where I can find a good template for a real estate opreating agreement? 

These two should easily provide the level of coverage you need to protect the assets you have including your personal property equity.  

Let us know what you find out!

If you find someone offering 15% the rate will be about 1% higher.  

Looking at the data you provided for Melbourne, FL:- Average rent is around $2,000-$2,100- Rents have actually decreased slightly year-over-year- There's a wide range of rental prices ($650 to $6,500)This suggests a diverse market with potential opportunities, but also some volatility.

I’m struggling to find good data on MTRs.

if you want something similar but lower risk, try to find something owned free and clear.