Your offer to purchase should include a requirement that the Seller provide all documentation and agree to sign an estoppel certificate (also called an estoppel form or agreement).

The screening they offer works well. 

I responded to her FSBO ad and made my offer which she happily accepted: a 36 month lease option; I'll bring her mortgage current, (1 month, $800), and continue making the monthly payments; option to purchase price of $88K, (my estimate of value, $100K); and I had the right to buy, sell, sublet, or assign the property at any time during the 36 months.

If you are willing to put down a larger down payment it might make sense with the flexible underwriting they offer, especially if you are going to run it as a MTR. 

Have you received any offers at all?

You'll also receive a lower ranking on Airbnb and other listing sites because you don't offer an amenity that everyone else in the area has. 

Understand that real estate is typically not a get rich quick scheme… $300-500/month per door is probably considered pretty good for profit on a financed property… so if you wanted to net $5,000/month and do it at $500/door you are going to need 10 doors.  

View of SF Bay2.40M (1st appraisal) 2.45M LIST (+400K) = 2.855M OFFER2.65M (2nd appraisal) 2.70M LIST (+400K) = 3.15M OFFER ??

Typically, when we close with a conventional lender there is paperwork we sign that states we intend to occupy the house for at least a year.  

It's all about what you have to offer.