I’ve been burned before so I’m extra cautious this time around.

I was taken aback by the sheer Income potential that was compounding in someone else’s account while I was sitting on their balcony...the calendar was booked the week before me, and the week after we were set to leave...assuming everyone paid the same rate I did...I was blown away by the $6000/month earning potential...Does anyone here have experience  with this sort of real estate investing? 

If this is the case - you may not be required to pay state taxes on the interest earned.You should compare the interest you earn on the deal with a muni bond that you can invest in.

Also Earn 18 % Interest while you hold the Certificate"..."

I guess a follow up question I didn’t know I had would be: so When your home goes up in value ($100k over 2 yrs in your example), and you only have 25% equity after 2 years (20% from down payment + 5% from extra 2 years of paying down), does that mean that you now have equity worth $100k (25% of $400k purchase price) or $125k (25% of $500k market value)?

Kind of like a stock many people overpay up front to buy for forward earnings not today's earnings. 

How would you spend your "extra" time at work?

I would happily spend the extra couple thousand dollars to avoid this.

I'm finishing a 4th bedroom and bath not just to get extra rent but to also be able to learn how to appraise and estimate costs in a controlled manner. 

I went with taking the extra 10K and having a lower cash flow.