Then just took off market at end Dec'20.

At end of 30 years, they could have already gotten the house free and clear, plus the 750k plus whatever they saved, to live the next 20-30 years, if they are smart, they will simply start taking equity from the house to live a normal life.

First of all, tenants in SFH have a tendency to stay for many years.

It does have a tendency to take too much of your income producing time and can make you not to want to answer the phone because of the fear that might exist in you.  

I dont have much advice for you or tons of banking "guidline or regulations" info for you, but i would like to give me 2 cents.the 1st sfh i bought, the loan was through a local "small" bank. they required 20% down and I funded all repairs. 5 year loan/20 year amortization with balloon payment at end. this puts me at about 33% equity and cashflowing nicely. after 1 year (will be in April), I plan on refinaincing, leaving 20% equity. not sure if i am going to do a 15 or 30 year note, but i should get most of this cash back out and still be cashflowing nicely. fast forward to my second deal. i needed to close within 10 days around Christmas time.

Similarly, colleagues, friends, and the media have a tendency to characterize 'retirement' investing.

I have a tendency to do that with things I find silly. 

But I will ask her to keep her eyes and ears open to see if someone would do that.On the other hand, here's something that I came up with while talking to her:We purchased the house for: $410,000Lease Option to Purchase - 5 Yr Lease - To be Sold @ $325,000 in 2013.Monthly Lease: $2850Credit toward Purchase price: $1050Actual Rent: $1800 (no rent increase for 5 years is a deal I am planning to strike here)Option Fee: $5000Price at end of Lease: $262,000Savings we need at end of lease: $150,000Owner gets a good down payment and financing.

They have a tendency to sweat .

That would have a tendency to drive someone to find a deal that woud benefit you and the dealfinder.